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Associate Professor at the University of Notre Dame

Book Cover: In Our Interest by Alexander Kustov

What is Populism Good for? An Experimental Test of Mobilization Effects

What is Populism Good for? An Experimental Test of Mobilization Effects

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Authors: Alexander Kustov and Yaoyao Dai

Journal: Research & Politics 13(1) (2026)

DOI: 10.1177/20531680261434109

Abstract

In recent decades, populist parties and candidates have gained increasing electoral support across the world. Despite this evident electoral success of populists, however, recent experimental studies find limited effects of populist rhetoric alone on vote choice. If such rhetoric is not effective in shaping voting preference, why would politicians adopt it, and what might explain the electoral success of populist candidates and parties? We argue that populism might influence elections through increasing turnout instead of or in addition to changing voters’ preference for candidates. However, existing conjoint and vignette survey experiments generally focus on forced candidate choice, which assumes full mobilization, potentially biasing the between-candidate choice estimates and missing abstention decisions important in real-world politics. To address this, we conducted a large-scale U.S. conjoint experiment of campaign messaging with an explicit abstention option to test for the possible mobilization effects of populism independent of persuasion effects and the various associated policy positions. Our results show that while populist rhetoric has limited persuasive impact, it can slightly increase mobilization, especially among voters who already hold populist views. Overall, however, voters’ alignment with candidates’ policy positions matters far more for both vote choice and turnout than the use of populist messaging itself.

Introduction

In recent decades, populist parties and candidates have gained increasing electoral support across the world, including the United States. Populists portray politics as conflicts between two homogeneous groups, the good people versus the corrupt elites, and claim that the people should be the only legitimate source of power. Populism and its adherents pose a direct challenge to pluralism and liberal democracy [@Mudde2018]. When politics is portrayed as a moral conflict between good and evil, there is no space for opposition or diverse points of view. As such, it is important to understand the effects of populism on electoral politics. However, despite the electoral success of populist parties and candidates, recent experimental studies find limited persuasion effects of populism on individual vote choice [@neuner2020populist; @Neuner2022; @Dai2023; @Ferrari2024; @Kittel2024; @Kollberg_2025]. Furthermore, even voters who endorse populist views do not seem to be more supportive of populist candidates than non-populists. These null findings in experimental studies contrast sharply with populists’ real-world electoral gains, creating a puzzle: if populist rhetoric does not systematically convert voters based on policy preferences, what explains its electoral success?

As a potential explanation, we argue that populism might influence elections through increasing turnout instead of or in addition to changing voters’ preference for candidates. One challenge to evaluate the effects of populism is that populism does not provide clear policy positions and thus always has to be combined with other “hosting ideologies” across the political spectrum from nationalism to socialism [@Mudde2004]. As a result, it is hard to evaluate whether and to what extent the electoral success of populists is due to their use of populism per se or particular combinations of populism and related policy positions. [note: In fact, it is common to wrongly associate the electoral effects of populism with its hosting ideologies and policies like candidates’ opposition to immigration [@hunger2022s; @Dai2023].] On the other hand, existing conjoint experiments that seperate populism from its hosting ideology focus on forced candidate choice, assuming full turnout. This may bias the between-candidate choice estimates and miss abstention decisions important in real-world politics [@miller2024preferential]. We, therefore, design a new large-scale U.S. conjoint experiment of campaign messaging to test the mobilization effects (turnout) of populism in addition to the persuasion effects (vote choice) with an additional abstain option. Testing mobilization effects is crucial for understanding populism’s implications for democratic politics. The proposed experimental study will thus help adjudicate debates about populism’s effects on participation and advance methodological understanding of forced choice conjoint experiments and their limitations.

By examining both mobilization and persuasion effects, our study seeks to clarify populism’s implications for democratic participation and electoral competition. Including an abstention option allows us to observe how populist messaging might shape turnout intentions within a realistic choice framework, even among relatively engaged survey respondents. This approach thereby extends our understanding of populism’s potential to mobilize voters-a dynamic that may emerge regardless of respondents’ actual turnout histories.

Our large-scale, preregistered U.S. conjoint experiment replicates prior findings of limited persuasive effects of populist rhetoric but also finds modest mobilization effects. In general, populist rhetoric increases the likelihood of voting. Specifically, populist rhetoric increases the likelihood of voting when used by candidates who share the respondent’s policy preferences, and especially among voters with populist attitudes. However, we find no evidence that it demobilizes non-populist voters. These results clarify when and for whom populism increases participation.

Persuasion versus Mobilization Effects of Populism

As one of the most contested concepts in the social sciences, scholars have historically adopted different conceptualizations of populism. In the political-strategic conceptualization, populism is a mobilization strategy used by personalistic leaders who seek to govern based on a direct, unmediated, and uninstitutionalized relationship with their supporters [@weyland2001clarifying; @weyland2017; @roberts2006; @levitsky2011conclusion]. In the sociocultural conceptualization, populism is performative and involves political actors flaunting an improper or `low’ style of politics that is intended to shock and build a close rapport with their supporters [@Moffitt:2016; @ostiguy2017socio]. According to the economic conceptualization, populism involves adopting unsustainable economic policies that are popular but ultimately hurt the interests of the majority [@dornbusch1991macroeconomics; @acemoglu2013political].

While these different approaches to conceptualizing populism offer valuable insights into different aspects of populism, they have been criticized for their lack of clarity and for the fact that they tend to emphasize features that are not shared by all forms of populism around the globe [@gidron2013; @Bonikowski2016multiple; @mudde2017populism; @mudde2018studying; @hawkins2018concept]. Partly in response to these critiques, there has been a growing consensus across disciplines on the adoption of a more minimalist ideational conceptualization of populism that focuses on populism’s core features [@mudde2004populist; @mudde2007populist; @mudde2017populism; @hawkins2017ideational; @hawkins2018ideational], considering it a set of ideas portraying politics as a moral conflict between the pure people and the corrupt elites [@Mudde2004; @Mudde2018]. According to this understanding, populism is a multidimensional concept with three necessary and jointly sufficient dimensions: people-centrism, anti-elitism, and anti-pluralism [@hawkins2018ideational; @Mudde2004].

People-centrism posits that people should be the sole source of legitimate political power. Although liberal democracy also embraces people-centrism, populism’s understanding of the “people” diverges from the pluralist perspective in liberal democracy. In populism, the “people” are perceived as a homogeneous entity with a unified will. Similarly, the “elite” in populism transcends mere membership in the establishment. As the morally corrupt antithesis of the “pure people,” the “elite” is portrayed as a malevolent force deliberately undermining the people’s interests. Since the distinction between the people and the elite in populism is fundamentally moralistic, an anti-elitist message must thus also be morally charged to qualify as populist [@Bonikowski2015; @mudde2017populism; @bonikowski2023populism].

Despite the evident success of populists, however, several recent experimental studies that separate populism from its hosting ideologies have found limited effects of populism alone on vote choice. For example, using a nationally representative sample in Germany, [@neuner2020populist] find that anti-immigration and pro-redistribution policy positions have much larger effects in attracting votes than populist priorities. In the U.S. context, recent survey experiments during different administrations find that populist rhetoric does not sway vote choice independent of policy positions [@Neuner2022; @Dai2023]. These studies also find that populist voters are not more likely to support populist candidates than non-populist voters. A recent study by [@Ferrari2024] corroborates these general results and provides some qualified evidence that the use of “thin” populist rhetoric can be beneficial in conjunction with “thick” right-wing policy positions but only among voters who already hold populist attitudes and self-identify as right-wing.

While studies show populist rhetoric (unlike policy positioning) alone doesn’t influence candidate choice in surveys, it may still influence electoral outcomes by influencing voters’ decision to vote and their political participation in general. This aligns with the literatures highlighting campaigns’ mobilization effects in resolving the “paradox of (not) voting” [@palfrey1985voter; @morton1991groups; @uhlaner1989rational] and populism’s mobilization potential [@Huber2017; @Weyland2001; @Immerzeel2015; @Hameleers2018; @morelli2021mobilization].

Many factors might influence voters’ decision to vote, such as the costs associated with (not) voting, the importance of an election, the linkage between a voter and a party [@powell1986american; @blais2006affects]. Empirically, electoral institutions that impose higher costs for not voting and facilitate more congruent voter-party linkage, such as compulsory voting and PR systems, generally lead to higher turnout [@cancela2016explaining; @green2013field]. While populist campaigns do not directly change the costs of voting or abstaining, they can influence voters’ calculation about voting by increasing the perceived importance of an election and improving the congruence or linkage between the party/candidate and the voters.

Populists often emphasize threats to “the people” (the virtuous in-group) from the elite establishment or ethnic minorities (the corrupt out-groups). They portray the in-group as an overlooked majority of ordinary citizens betrayed by elites, framing elections as opportunities to reclaim popular sovereignty. Those identifying with this “silent majority” are thus more likely to view the election as high-stakes, increasing their likelihood to vote or engage in other political activities [@simon2001politicized].

The populist framing of the “silent majority” and the “corrupt elites” can also increase the perceived congruence between the candidate and the voters who identify as one of the majority and those who distrust the current institutions. Individuals with populist attitudes tend to feel more alienated from the mainstream parties and are also less likely to turn out and vote [@gidron2020populism; @anduiza2019populism]. Voters with populist attitudes and voters who distrust the political system might find populist candidates and parties more appealing in terms of representing their interests. Indeed, [@guiso2017populism] find that voters who distrust the political system tend to vote less and tend to vote for a populist party when it is an option in Europe.

In addition to the spread of people-centric and anti-elitist ideas, populist campaigns are also always morally charged. This is important because political psychology research reveals that politicians’ use of moral rhetoric can mobilize those already aligned with their positions [@Jung2020]. Recently, [@Kollberg2024] confirmed this applies to populist rhetoric as well, which can effectively rally supporters but hinder efforts to expand electoral support [@Blumenau2024]. However, just as campaign strategies have different (de)moblization effects on specific subsets of voters [@lau2009negative; @hersh2013targeted], we expect populist campaigns to also work differently among subsets of voters. Specifically, populist rhetoric should only mobilize those who already support a candidate and find the messaging appealing. Otherwise, it may backfire [@Kollberg2024].

{1} Empirically, observational studies on the link between populist parties in parliament and overall turnout yield mixed results at the aggregated level [@Huber2017; @Leininger2021]. The same holds true for turnout among specific groups, including those with populist attitudes [@Immerzeel2015]. The inconclusive findings further suggest that the potential mobilization effects, if they exist, are going to depend on the hosting ideologies (policy positions) of populist campaigns and the type of voters they are targeting.

Hypotheses

To address the apparent paradox of populism’s electoral success despite its limited persuasion effects, we aim to, for the first time, explicitly test for its possible mobilization effects in a survey experiment. Based on the research discussed above, we argue that the effects of candidates’ use of populist rhetoric on voter turnout primarily depend on two factors: (1) voters’ own positivity or negativity toward populism and (2) the congruence between voters’ policy positions and those of the candidates [@Graham2020a; @silva2022populism; @Dai2023; @Ferrari2024].

As our background expectation, we consider the availability of congruent policy positions among candidates as the main factor influencing both individuals’ vote choice and turnout:

H0: Individuals are more likely to vote (less likely to abstain) in a two-candidate election when at least one of the available candidates has congruent policy positions shared with them (as opposed to both candidates having non-congruent positions).

For our main confirmatory tests, we focus on populist rhetoric as a potentially important driver of voters’ mobilization. While the use of populist rhetoric in a campaign might not change voters’ preference for a certain candidate, it might still potentially influence their likelihood of voting for their preferred (policy-congruent) candidate in the first place. In particular, we consider a typical two-candidate race where voters have at least one preferred candidate and argue that the use of populist rhetoric in campaign messaging would likely mobilize voters who already hold populist attitudes and demobilize those who do not when used by that preferred candidate. Importantly, populism is likely only going to be (de)mobilizing when it is used by voters’ preferred candidate with congruent policy positions. We thus put forward the following two main hypotheses:

H1: Populist individuals are more likely to vote (less likely to abstain) in a two-candidate election when their policy-congruent candidate uses populist rhetoric (as opposed to non-populist rhetoric, regardless of whether there is one or two congruent candidates and regardless of the non-congruent candidate’s use of populist rhetoric).

H2: Non-populist individuals are more likely to vote (less likely to abstain) in a two-candidate election when their policy-congruent candidate uses non-populist rhetoric (as opposed to populist rhetoric, regardless of whether there is one or two congruent candidates and regardless of the non-congruent candidate’s use of populist rhetoric).

Altogether, our two conditional hypotheses imply that net mobilization effects and the net electoral benefits for particular candidates likely depend on the distribution of populist voters among their supporters and opponents in a particular political context. Still, given the majority support for at least some components of populism in contemporary politics [@wuttke2020whole], we can also specify a more general hypothesis about the likely average mobilization effects of using populist rhetoric by any candidate:

H3: Individuals are more likely to vote (less likely to abstain) in a two-candidate election when at least one of the available candidates uses populist rhetoric (as opposed to both candidates using non-populist rhetoric).

Data and Methods

Expanding the recent conjoint experiments by [@Dai2023], [@Neuner2022], and [@Ferrari2024], we recruit a well-powered (90%+) online US sample (N = 3502 / 28016) approximating national demographics through Prolific. [note: Following our pre-registered analysis plan, no additional attention checks or other quality control filters are used to screen the participants in the target sample and all analyses are conducted on the full sample using all conjoint tasks with non-missing outcome data. When estimating effects on the subgroups, we use listwise deletion in cases when the data on the relevant subgroup covariates (policy congruence or populist attitudes) is missing.] While the two-party system in the U.S. provides fewer opportunities for organized populist parties, it still provides ample opportunities for populist candidates [@Lee2019]. In fact, scholars find that populist communication can be a strategic choice by candidates from all parties in the U.S. [@dai2022politicians; @Bonikowski2015].

Following [@Dai2023], we embed the core elements of populist rhetoric in realist campaign messages, which mimic the type of information voters receive during elections. Unlike some other previous studies that only included various populist attributes [@Neuner2022; @silva2022populism], we also explicitly specify the non-populist, liberal democratic rhetoric as the baseline group for experimental comparison.

We adopt the ideational approach to operationalize liberal democracy and populism as multi-dimensional concepts, focusing on the core dimensions of (anti-pluralist) people-centrism and (moralized) anti-elitism as conjoint choice experiment attributes [@mudde2017populism; @Mudde2018; @wuttke2020whole]. While both populist and liberal democratic forms of communication are often people-centric and critical of elites, they differ in their portrayal of these groups. Populists view the people as homogeneous, morally good, and unified by a single popular will, thus adopting an anti-pluralist stance. In contrast, liberal democrats see the people as diverse, with conflicting interests, embracing pluralism. At the same time, populists perceive elites as a homogeneous group that is morally inferior. Consequently, anti-elitism in populism is inherently morally charged. [note: Although both liberal democratic and elitist rhetoric can theoretically oppose populism, explicitly pro-elitist communication is rare in modern democratic politics [@mudde2017populism]. Therefore, we include only liberal democratic rhetoric as “non-populist” campaign communication in our experiment.]

To separate populism from associated ideologies, we also include (randomized) immigration or economic policy positions as separate attributes independent from the populism attributes. These two issues have been most commonly associated with right- and left-wing populism, and have also been considered as “most important” by most US voters in recent years. [note: See the Gallup data at https://news.gallup.com/poll/1675/most-important-problem.aspx. Following [@Velez2024], we are also open to including a wider selection of issues as chosen by respondents if the reviewers believe this is necessary.]

Finally, we include questions to measure respondents’ populist attitudes using existing scales [@wuttke2020whole], as well as their agreement with various immigration and economic policy positions to measure policy congruence. While our main specifications rely on direct policy congruence, we also replicate our analysis based on partisanship congruence (where pro-immigration, left-leaning positions are considered congruent for Democratic respondents and anti-immigration, right-leaning positions are considered congruent for Republican respondents.

Given the recent call for “stimuli sampling” as an important complement to “participant sampling” to improve external validity [@Clifford2023], we also randomize the particular messaging we use to communicate each of our treatments. Instead of using the same exact phrases or words to indicate a moralistic anti-establishment statement, for instance, we generate a number (16) of distinct yet comparable messages mimicking real campaigns. [note: Given that the minimalist definition of populism is quite abstract, to increase the realisticness of the treatments, we identify and paraphrase messages from the past U.S. presidential campaigns that satisfy the definition of each core component of populism. However, it is still uncommon for politicians to employ the full populist rhetoric at high density, as in the treatments [@dai2022politicians].] We also randomize whether candidates state their positions on economic or immigration policy in each message pair. In turn, this should improve the realism and generalizability of our experiment. For the list of all attributes and their implementation, see Table tab:Conjoint_attributes. Importantly, our experimental design does not make any constraints based on candidate congruency: respondents will be randomly exposed to profiles in which both, one, or neither candidate is policy-congruent. For more details, see our Design Table tab:Design_table.

Overall, our conjoint design replicate the forced choice paired-profile design by [@Dai2023] with campaign messages of 8 candidate pairs in the US House general election setting, as well as extend it with an additional abstain option. The abstain option gives respondents an opportunity to indicate their non-preference, which arguably makes the experiment more realistic and allows us to test the mobilization effect of populist campaigns. Following prior literature, we decided not to include explicit party labels in either version of the conjoint design, as they would otherwise dominate all other attributes [@silva2022populism]. Below, we present the vignette instruction for the conjoint experiment with an abstention option, which includes the context of the hypothetical election and the task summary. Information in brackets are the two contexts we randomly assign to respondents.

The next election for the US House of Representatives will be held later in November 2026. In the next few minutes, we are going to describe eight pairs of potential candidates running for an open seat in your district. For each candidate, we will show you his or her background and campaign message highlights. Please indicate which candidate you would vote for in the upcoming elections. If neither candidate appeals to you and you would prefer not to vote at all, please choose the abstain option. Please remember that we are interested in your personal opinion. There are no right' or wrong’ answers.

Candidates’ backgrounds, campaign messages, and policy positions are embedded following the template below. Information in brackets are treatment attributes that are randomly assigned. For each of the rhetoric attributes, we include sixteen different versions/messages to increase the variation of campaign messages a respondent might receive. To maximize statistical power, we ensure all candidates use populist or non-populist rhetoric across both dimensions (i.e., use anti-pluralist and moralist or pluralist and non-moralist rhetoric). We also randomize whether a particular pair of candidates features their positions on immigration or the economy (but not both). For detailed attribute values and examples of candidate profiles and messages, see Online Appendix.

Candidate [A / B] worked as a [elite: state official / government advisor / businessman / lawyer / professor / journalist / banker / executive; non-elite: social worker / teacher / firefighter / farmer / nurse / mechanic / retail worker / carpenter] before running and has [never held office before; held office for many years]. Campaign highlights: “[Anti-pluralist; Pluralist] AND [Moralist; Non-moralist]. [Anti-immigration; pro-immigration] OR [Right-leaning economic policy; left-leaning economic policy].”

After viewing each pair of candidate messages, the respondents are asked to indicate their subjective likelihood of voting for both candidates: “How likely is it that you would vote for someone like Candidate A and Candidate B in the upcoming election?” [Very likely, Somewhat likely, Neither Likely nor unlikely, Somewhat unlikely, Very unlikely]. They then indicate their (forced) choice response in the following prompt: “If these were the candidates in an upcoming election in your district, what would you do?” [I would vote for Candidate A / I would vote for Candidate B / I would abstain and not vote]. According to [@miller2024preferential], a non-trivial proportion of US respondents might be expected to choose to abstain if given the option, highlighting the importance of considering abstention in conjoint experiments studying voter preferences.

Analysis and Results

In line with previous conjoint analyses that introduce an abstain option in candidate choice, our sample shows that 11% of respondents abstained in the first conjoint task (16% on average across all conjoint tasks). Notably, this is close to the (clearly underreported) 14% of respondents who self-reported abstaining in the 2024 election in our survey. The positive correlation between 2024 abstention and average choice experiment abstention (r = 0.21) further indicates that people’s hypothetical conjoint choices may be reflective of their voting behavior.

We first replicate the main analysis of [@Dai2023] and test the effects of populist rhetoric on vote choice at the candidate-profile level. Consistent with their theoretical argument, we find that candidates with populist speech attributes are statistically more likely to be selected, especially among populist voters, though the effects are substantively very small. In line with their substantive results, we also find that these effects of rhetorical choices are completely trumped by those of candidates’ substantive policy positions. Detailed results are included in Table tab:rep of Online Appendix.

Our main results on the mobilization effects of populism are summarized in Figure 1-3 below. Given that our focus is on mobilization rather than persuasion, all hypotheses are tested at the more appropriate level of candidate pair rather than individual profile [@Clayton2023] by regressing the turnout/abstention outcome for each pair by the respondent on relevant conjoint pair attributes (with abstention coded as 1 and 0 otherwise, including voting for either candidate). As can be seen in Figure fig:H0H3, consistent with H0, the probability of voting (instead of abstaining) in a hypothetical electoral contest is 27.4 percentage points higher when at least one candidate shares a congruent policy position with the respondent. The effect is both statistically significant and substantively large. At the same time, consistent with H3, having at least one populist candidate is associated with a 1.5 percentage point increase in the probability of voting. While statistically significant, the mobilizing effect of populist rhetoric is substantively small.

Figure: Mobilization Effects of Policy Congruency (H0) and Populist Rhetoric (H3)

Mobilization Effects of Policy Congruency (H0) and Populist Rhetoric (H3)

Caption: Mobilization Effects of Policy Congruency (H0) and Populist Rhetoric (H3)

To test the heterogeneous effects of populist rhetoric among populist and non-populist voters (H1 and H2), we estimate three models (Table tab:h12), one using the populist group, one using the non-populist group, and one interaction model on all respondents. Since H1 and H2 concern the policy congruent candidate’s usage of populist rhetoric, following our pre-registered analysis plan, we restrict the data to having at least one policy congruent candidate in a pair of candidates. We visualize the AMCEs of populist speech attributes compared to non-populist (liberal democratic) attributes estimated from the interaction model in Figure fig:H1H2. We find that while, in line with H1, populist voters are statistically more likely to vote when their policy congruent candidate uses populist rhetoric, this effect is substantively small. Furthermore, contrary to H2, we do not find any demobilizing effects of using populist rhetoric among non-populist voters. We replicate our main analyses using an alternative operationalization of congruence using partisanship instead of respondents’ reported policy preference, with no change in the underlying results. We include results of those robustness checks in Tables tab:h03party and tab:h12party of Online Appendix.

Figure: Effects of Using Populist Rhetoric by Policy Congruent Candidate on Probability of Voting for Either Candidate among Populist and Non-Populist Respondents

Effects of Using Populist Rhetoric by Policy Congruent Candidate on Probability of Voting for Either Candidate among Populist and Non-Populist Respondents

Caption: Effects of Using Populist Rhetoric by Policy Congruent Candidate on Probability of Voting for Either Candidate among Populist and Non-Populist Respondents

We further visualize the exploratory tests for each of the possible combinations of populism and policy congruence at the candidate-pair level in Figure fig:H1H2exp. The condition in which neither candidate is policy congruent and neither uses populist rhetoric is treated as the baseline category. As expected under H0, having at least one policy congruent candidate in a pair significantly increases the respondent’s likelihood of voting. While we do not have theoretical expectations regarding the mobilizing effect of populism when it is used by a policy incongruent candidate, our exploratory analysis suggests that in the absence of a policy congruent candidate, populist rhetoric from either candidate increases the likelihood of voting regardless of whether the respondent holds populist attitudes.

Figure: Effects of Populist Rhetoric and Policy Congruence by Respondents’ Populism on Probability of Voting for Either Candidate (Exploratory)

Effects of Populist Rhetoric and Policy Congruence by Respondents' Populism on Probability of Voting for Either Candidate (Exploratory)

Caption: Effects of Populist Rhetoric and Policy Congruence by Respondents’ Populism on Probability of Voting for Either Candidate (Exploratory)

Conclusion

Consistent with earlier findings, we find that populist rhetoric has limited persuasive power relative to substantive policy positions. However, we also find evidence that populist rhetoric can slightly increase turnout-particularly among voters who hold populist attitudes and encounter a policy-congruent candidate using such rhetoric. On the other hand, non-populist voters do not seem to punish their policy-congruent candidates when they use populist rhetoric. These results suggest that while populism is not a broadly effective persuasive style, it may still function as a low cost mobilization tool for aligned voters, which can be consequential in close elections. Overall, as shown in our analyses, the congruence of substantive positions outweighs any effects of populist rhetoric on both vote choice and mobilization among populist and non-populist voters alike.

Given these limited direct effects of populist rhetoric on persuasion and mobilization, future research could explore its potential indirect effects-for example, how such rhetoric might attract disproportionate media coverage among journalists in increasingly polarized political environments [@manucci2017populism]. At the same time, given the implemented extensions to previous designs and the addition of the abstention choices, our results also contribute to a better methodological understanding of increasingly popular (forced choice) conjoint experiments and their potential limitations. Beyond academia, political practitioners could also benefit from an improved understanding of populism’s effectiveness in campaign messaging.

While our study provides insights into the mobilization and persuasion effects of populist rhetoric, it has limitations that future research should address. First, our experiment is conducted within the U.S. two-party system, where voters face fewer electoral options than in multi-party contexts. Populism’s mobilization effects may differ where alternative parties provide additional outlets for dissatisfaction. Future research should test whether our findings replicate in such systems. Second, our design follows the minimalist ideational conceptualization of populism and abstracts away from candidate-specific factors that are emphasized by other conceptualization approaches, presenting populist rhetoric in a controlled textual format. For example, since populism can also be closely tied to personalistic leadership, the speaker’s characteristics may influence its effectiveness [@weyland2024democracy]. Future studies could incorporate audio-visual stimuli to better capture the charisma component of populist appeals. These extensions would further clarify how populism influences electoral behavior.

Included file: appendix_r3

Source Appendix: appendix_r3.tex

Online Appendix

Power Analysis

Given that we are testing the interaction effects between populist rhetoric, attitudes, and related policy positions at the level of a candidate choice pair for the outcome of abstention, a larger than usual sample is needed. For the purposes of our setup, we assume that our respondents effectively choose between one profile-pair combination in each task with 4 possible levels for each conjoint attribute [@miller2024preferential]. That is, every time respondents see a pair of campaign messages and decide whether to vote or not, it is a function of whether, for example, candidate A and B use populist rhetoric or not with four possible combinations (both are populist, neither is populist, only A is populist, only B is populist).

Based on our power analysis [@schuessler2020power], the proposed sample size (3,500 x 8 candidate choice pairs = 28,000) provides $>99%$ statistical power to detect a small effect of substantive significance (AMCE = 0.05) and $>95%$ statistical power to detect a very small effect $<$ 0.03 for any of the target 2-level attributes at $alpha = 0.05$ for H0/H3 with a near zero probability that estimated coefficients have incorrect signs given the baseline voting rate of 70% [@miller2024preferential]. To test our main hypotheses (H1/H2) that imply a possible interaction of one of the candidates using populist rhetoric and voters’ populist attitudes, given the availability of any policy congruent candidates ($3/4$), as well as the expected distribution of populist attitudes ($ 1/2$), our design can reliably detect interaction effects greater than 0.05 with $>90%$ power. \

Tables

Table: Descriptive Statistics (Prolific, n = 3502/28016)

\begin{table}[!htbp] \centering \caption{Descriptive Statistics (Prolific, n = 3502/28016)} \label{tab:descriptive} \begin{tabular}{@{\extracolsep{5pt}}lcccccc} \\[-1.8ex]\hline \hline \\[-1.8ex] Statistic & \multicolumn{1}{c}{Mean} & \multicolumn{1}{c}{St. Dev.} & \multicolumn{1}{c}{Min} & \multicolumn{1}{c}{Pctl(25)} & \multicolumn{1}{c}{Pctl(75)} & \multicolumn{1}{c}{Max} \\ \hline \\[-1.8ex] Female & 0.50 & 0.50 & 0 & 0 & 1 & 1 \\ College+ & 0.53 & 0.50 & 0 & 0 & 1 & 1 \\ Republican & 0.38 & 0.49 & 0 & 0 & 1 & 1 \\ Democrat & 0.48 & 0.50 & 0 & 0 & 1 & 1 \\ Populist & 0.52 & 0.50 & 0 & 0 & 1 & 1 \\ \hline \\[-1.8ex] \end{tabular} \end{table}

Table: Replication of [@dai2022politicians]

\begin{table}[!htbp] \centering \caption{Replication of \citet{dai2022politicians}} \label{tab:rep} \begin{tabular}{@{\extracolsep{2pt}}lccc} \\[-1.8ex]\hline \hline \\[-1.8ex] & \multicolumn{3}{c}{\textit{Dependent variable:}} \\ \cline{2-4} \\[-1.8ex] & \multicolumn{3}{c}{Probability of Selection} \\ \\[-1.8ex] & Populist Group & Non-populist Group & Full Sample\\ \hline \\[-1.8ex] Populist rhetoric & 0.047$^{***}$ & 0.019$^{**}$ & 0.019$^{**}$ \\ & (0.006) & (0.006) & (0.006) \\ Policy congruency & 0.313$^{***}$ & 0.325$^{***}$ & 0.319$^{***}$ \\ & (0.008) & (0.008) & (0.006) \\ Populist voter &  &  & 0.006 \\ &  &  & (0.005) \\ Populist rhetoric : Populist voter &  &  & 0.027$^{**}$ \\ &  &  & (0.009) \\ Constant & 0.248$^{***}$ & 0.235$^{***}$ & 0.239$^{***}$ \\ & (0.005) & (0.006) & (0.005) \\ \hline \\[-1.8ex] Observations & 26,806 & 24,464 & 51,270 \\ Adjusted R$^{2}$ & 0.102 & 0.110 & 0.106 \\ \hline \hline \\[-1.8ex] \end{tabular} \begin{flushleft} \footnotesize{Note: Robust standard errors clustered by respondent are given in parentheses, $^{*}$p$<$0.05; $^{**}$p$<$0.01; $^{***}$p$<$0.001.} \end{flushleft} \end{table}

Table: Effects of Candidate Pair Attributes on Probability of Voting for Either Candidate

\begin{table}[!htbp] \centering \caption{Effects of Candidate Pair Attributes on Probability of Voting for Either Candidate} \label{tab:h03} \begin{tabular}{@{\extracolsep{-3pt}}lcccc} \\[-1.8ex]\hline \hline \\[-1.8ex] & \multicolumn{4}{c}{\textit{Dependent variable:}} \\ \cline{2-5} \\[-1.8ex] & \multicolumn{4}{c}{Probability of Voting} \\ \\[-1.8ex] & (1) & (2) & (3) & (4)\\ \hline \\[-1.8ex] Policy congruent candidate(s) & 0.274$^{***}$ &  & 0.274$^{***}$ & 0.305$^{***}$ \\ & (0.008) &  & (0.008) & (0.014) \\ Populist candidate(s) &  & 0.016$^{**}$ & 0.015$^{**}$ & 0.046$^{**}$ \\ &  & (0.005) & (0.005) & (0.014) \\ Policy congruent candidate(s):Populist candidate(s) &  &  &  & $-$0.042$^{**}$ \\ &  &  &  & (0.015) \\ Constant & 0.631$^{***}$ & 0.827$^{***}$ & 0.620$^{***}$ & 0.597$^{***}$ \\ & (0.008) & (0.005) & (0.008) & (0.013) \\ \hline \\[-1.8ex] Observations & 25,635 & 28,016 & 25,635 & 25,635 \\ Adjusted R$^{2}$ & 0.103 & 0.0003 & 0.103 & 0.104 \\ \hline \hline \\[-1.8ex] \end{tabular} \begin{flushleft} \footnotesize{Note: Variables are measured at the candidate-pair level. The two independent variables measure whether there is at least one policy-congruent candidate and whether there is at least one populist candidate. The congruent candidate and the populist candidate might or might not be the same. Robust standard errors clustered by respondent are given in parentheses, $^{*}$p$<$0.05; $^{**}$p$<$0.01; $^{***}$p$<$0.001.} \end{flushleft} \end{table}

Table: Heterogeneous Effects of Populist Rhetoric by Policy Congruent Candidate

\begin{table}[!htbp] \centering \caption{Heterogeneous Effects of Populist Rhetoric by Policy Congruent Candidate} \label{tab:h12} \begin{tabular}{@{\extracolsep{-3pt}}lccc} \\[-1.8ex]\hline \hline \\[-1.8ex] & \multicolumn{3}{c}{\textit{Dependent variable:}} \\ \cline{2-4} \\[-1.8ex] & \multicolumn{3}{c}{Probability of Voting} \\ \\[-1.8ex] & Populist Group & Non-populist Group & All\\ \hline \\[-1.8ex] Congruent candidate(s) being populist & 0.013$^{*}$ & 0.001 & 0.001 \\ & (0.006) & (0.007) & (0.007) \\ Populist voter &  &  & 0.023$^{**}$ \\ &  &  & (0.009) \\ Populist congruent candidate:Populist voter &  &  & 0.012 \\ &  &  & (0.009) \\ Constant & 0.912$^{***}$ & 0.889$^{***}$ & 0.889$^{***}$ \\ & (0.005) & (0.007) & (0.007) \\ \hline \\[-1.8ex] Observations & 10,047 & 9,287 & 19,334 \\ Adjusted R$^{2}$ & 0.0004 & $-$0.0001 & 0.003 \\ \hline \hline \\[-1.8ex] \end{tabular} \begin{flushleft} \footnotesize{Note: The table shows the AMCEs of the randomly assigned policy congruency and populist speech attributes on the probability of mobilizing voters to vote instead of abstaining. Sample is restricted to pairs with at least one policy congruent candidate. Robust standard errors clustered by respondent are given in parentheses, $^{*}$p$<$0.05; $^{**}$p$<$0.01; $^{***}$p$<$0.001.} \end{flushleft} \end{table}

Table: Heterogeneous Effects of Candidate Pair Attributes on Probability of Voting for Either Candidate

\begin{table}[!htbp] \centering \caption{Heterogeneous Effects of Candidate Pair Attributes on Probability of Voting for Either Candidate} \label{tab:expgroups} \begin{tabular}{@{\extracolsep{-3pt}}lccc} \\[-1.8ex]\hline \hline \\[-1.8ex] & \multicolumn{3}{c}{\textit{Dependent variable:}} \\ \cline{2-4} \\[-1.8ex] & \multicolumn{3}{c}{Probability of Voting} \\ & Populist Voter & Non-populist Voter & All Voters \\ \\[-1.8ex] & (1) & (2) & (3)\\ \hline \\[-1.8ex] One candidate congruent and populist & 0.305$^{***}$ & 0.326$^{***}$ & 0.314$^{***}$ \\ & (0.014) & (0.016) & (0.011) \\ One candidate congruent and non-populist & 0.281$^{***}$ & 0.328$^{***}$ & 0.303$^{***}$ \\ & (0.014) & (0.016) & (0.011) \\ One candidate congruent and neither populist & 0.294$^{***}$ & 0.329$^{***}$ & 0.310$^{***}$ \\ & (0.014) & (0.016) & (0.011) \\ One candidate congruent and both populist & 0.294$^{***}$ & 0.329$^{***}$ & 0.310$^{***}$ \\ & (0.014) & (0.016) & (0.011) \\ Neither candidates congruent and one populist & 0.040$^{**}$ & 0.057$^{***}$ & 0.048$^{***}$ \\ & (0.014) & (0.016) & (0.011) \\ Neither candidates congruent and both populist & 0.051$^{**}$ & 0.031 & 0.042$^{***}$ \\ & (0.016) & (0.019) & (0.012) \\ Both candidates congruent and both non-populist & 0.271$^{***}$ & 0.324$^{***}$ & 0.296$^{***}$ \\ & (0.016) & (0.019) & (0.012) \\ Both candidates congruent and one populist & 0.289$^{***}$ & 0.337$^{***}$ & 0.311$^{***}$ \\ & (0.014) & (0.016) & (0.011) \\ Both candidates congruent and both populist & 0.301$^{***}$ & 0.320$^{***}$ & 0.310$^{***}$ \\ & (0.016) & (0.019) & (0.012) \\ Constant & 0.628$^{***}$ & 0.561$^{***}$ & 0.597$^{***}$ \\ & (0.011) & (0.013) & (0.009) \\ \hline \\[-1.8ex] Observations & 13,403 & 12,232 & 25,635 \\ Adjusted R$^{2}$ & 0.102 & 0.106 & 0.104 \\ \hline \hline \\[-1.8ex] \end{tabular} \begin{flushleft} \footnotesize{Note: Categories are mutually exclusive with "Neither candidate congruent and neither populist" as the baseline categories. $^{*}$p$<$0.05; $^{**}$p$<$0.01; $^{***}$p$<$0.001.} \end{flushleft} \end{table}

Table: Effects of Candidate Pair Attributes on Probability of Voting for Either Candidate (Robustness test using party-congruence)

\begin{table}[!htbp] \centering \caption{Effects of Candidate Pair Attributes on Probability of Voting for Either Candidate (Robustness test using party-congruence)} \label{tab:h03party} \begin{tabular}{@{\extracolsep{-5pt}}lcccc} \\[-1.8ex]\hline \hline \\[-1.8ex] & \multicolumn{4}{c}{\textit{Dependent variable:}} \\ \cline{2-5} \\[-1.8ex] & \multicolumn{4}{c}{Probability of Voting} \\ \\[-1.8ex] & (1) & (2) & (3) & (4)\\ \hline \\[-1.8ex] Party Congruent candidate(s) & 0.244$^{***}$ &  & 0.244$^{***}$ & 0.276$^{***}$ \\ & (0.008) &  & (0.008) & (0.013) \\ Populist candidate(s) &  & 0.016$^{**}$ & 0.013$^{*}$ & 0.045$^{***}$ \\ &  & (0.005) & (0.005) & (0.014) \\ Party congruent candidate(s):Populist candidate(s) &  &  &  & $-$0.044$^{**}$ \\ &  &  &  & (0.015) \\ Constant & 0.665$^{***}$ & 0.827$^{***}$ & 0.656$^{***}$ & 0.632$^{***}$ \\ & (0.007) & (0.005) & (0.008) & (0.013) \\ \hline \\[-1.8ex] Observations & 26,296 & 28,016 & 26,296 & 26,296 \\ Adjusted R$^{2}$ & 0.086 & 0.0003 & 0.086 & 0.087 \\ \hline \hline \\[-1.8ex] \end{tabular} \begin{flushleft} \footnotesize{Note: Robust standard errors clustered by respondent are given in parentheses, $^{*}$p$<$0.05; $^{**}$p$<$0.01; $^{***}$p$<$0.001.} \end{flushleft} \end{table}

Table: Heterogeneous Effects of Populist Rhetoric by Party Congruent Candidate ((Robustness test using party-congruence))

\begin{table}[!htbp] \centering \caption{Heterogeneous Effects of Populist Rhetoric by Party Congruent Candidate ((Robustness test using party-congruence))} \label{tab:h12party} \begin{tabular}{@{\extracolsep{-3pt}}lccc} \\[-1.8ex]\hline \hline \\[-1.8ex] & \multicolumn{3}{c}{\textit{Dependent variable:}} \\ \cline{2-4} \\[-1.8ex] & \multicolumn{3}{c}{Probability of Voting} \\ \\[-1.8ex] & Populist Voter  & Non-populist Voter  & All\\ \hline \\[-1.8ex] Congruent candidate(s) being populist & 0.004 & $-$0.005 & $-$0.005 \\ & (0.005) & (0.006) & (0.006) \\ Populist voter &  &  & 0.018$^{*}$ \\ &  &  & (0.008) \\ Populist congruent candidate:Populist voter &  &  & 0.008 \\ &  &  & (0.008) \\ Constant & 0.918$^{***}$ & 0.900$^{***}$ & 0.900$^{***}$ \\ & (0.005) & (0.006) & (0.006) \\ \hline \\[-1.8ex] Observations & 10,325 & 9,478 & 19,803 \\ Adjusted R$^{2}$ & $-$0.0001 & $-$0.0001 & 0.001 \\ \hline \hline \\[-1.8ex] \multicolumn{4}{r}{} \\ \end{tabular} \begin{flushleft} \footnotesize{Note: The table shows the heterogeneous effects of populist campaign by candidate with congruent policy positions among populist and non-populist groups of respondents. Sample is restricted to pairs with at least one policy congruent candidate. Robust standard errors clustered by respondent are given in parentheses, $^{*}$p$<$0.05; $^{**}$p$<$0.01; $^{***}$p$<$0.001.} \end{flushleft} \end{table}

Table: List of Conjoint Attributes

\begin{table}[!htbp] \centering \caption{List of Conjoint Attributes} \label{tab:Conjoint_attributes} \vspace*{-25pt} \includegraphics[width=\linewidth]{TableA1_r2.pdf} \vspace*{-25pt} \end{table}

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Table: Design Table

\begin{table}[!htbp] \centering \caption{Design Table} \label{tab:Design_table} \vspace*{-25pt} \includegraphics[width=\textwidth]{TableA2.pdf} \vspace*{-25pt} \end{table}

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Vignette Instruction

Below, we present the vignette instructions for the conjoint experiment with an abstention option, including the context of the hypothetical election and the task summary. Information in brackets are the two contexts we randomly assign to respondents.

The next election for the US House of Representatives will be held later in November 2026. In the next few minutes, we are going to describe eight pairs of potential candidates running for an open seat in your district. For each candidate, we will show you his or her background and campaign message highlights. Please indicate which candidate you would vote for in the upcoming elections. If neither candidate appeals to you and you would prefer not to vote at all, please choose the abstain option. Please remember that we are interested in your personal opinion. There are no right' or wrong’ answers.

Campaign Messaging Variants

*Anti-Pluralist People-centrism**:

  • I believe we, the people, share the same values and interests.
  • Politicians should follow the will of the people.
  • I believe the government is to respond to the will of the people.
  • I am running to represent the voice of the American people.
  • I am running to take back control of politics for the American people.
  • Control of politics needs to be returned to the American people.
  • The people, and not politicians, should make our most important policy decisions.
  • The strength of our nation comes from the hardworking virtuous people.
  • Our future lies in the hands of the common people.
  • This election isn’t about any individual; it’s about taking back control of politics for the people.
  • My goal is to serve and empower the true American people.
  • I believe the government should solely reflect and respond to the will of the people.
  • Together, we, the people, will shape a brighter future for our nation.
  • I am committed to putting the true American people first.
  • It’s time to restore power to the hands of the people where it rightfully belongs.
  • My priority is to ensure that the government serves the people, not the other way around.

*Pluralist People-centrism**:

  • I will make sure to listen to all the different voices of the people. [note: In implementing the experiment, this item was not presented. Pluralist people-centrism only had 15 variations. However, it should not affect the main analysis.]
  • I am running to defend all our rights, no matter our differences.
  • I believe it’s crucial to compromise between diverse viewpoints.
  • Trying to divide America between us and them is wrong, and we’re not going to let it work.
  • I believe a thriving democracy depends on the diverse voices of all the people.
  • In a democracy, it’s crucial to consider diverse viewpoints, and I’m committed to bridging our differences.
  • I believe we need to listen to the voices from all groups, even when we disagree with their opinion.
  • All groups deserve to be heard and represented in politics.
  • We should resolve our differences through conversations and compromises.
  • I believe a healthy democracy must protect the rights of both the majority and the minority.
  • People may have conflicting interests and differing opinions, but we should still hear their voices in politics.
  • Having different opinions and interests doesn’t imply that others are bad.
  • Our strength lies in our diversity, and I am committed to ensuring every voice is heard.
  • I will work to unite our communities and find common ground.
  • I believe in an inclusive America where everyone feels valued and respected.
  • Together, we can build a stronger nation by embracing our diversity.

*Moralist way of criticizing elites**:

  • But there’re bad people in Washington who don’t care about Americans.
  • Sadly, the corrupt Washington elites only listen to special interests.
  • Sadly, Congress is full of insiders who only care about themselves now.
  • I’ll protect Americans against all the wrongdoing in Washington.
  • The elites have disconnected from the needs of the people, prioritizing their own interests.
  • The elites have long ignored the struggles and voices of ordinary citizens.
  • It’s disheartening that Congress is dominated by self-serving individuals.
  • In their pursuit of personal gain, the elites sacrifice the welfare of ordinary people.
  • The rich and powerful few sacrifice the needs of the people for their own benefit.
  • Sadly, only the rich and powerful few are in control of politics.
  • Politics is dominated by the wealthy and powerful, putting their own interests above the people.
  • I will not tolerate any “special interests,” that put themselves above the people.
  • The corrupt elite have rigged the system against everyday Americans.
  • It’s time to hold the corrupt elite accountable.
  • The elite have betrayed the trust of the people, and it’s time for change.
  • We must break the grip of the self-serving elite and restore power to the people.

*Non-moralist way of criticizing elites**:

  • I’ll fix the problems in Washington caused by the ineffective government.
  • The current government has created more problems than it has solved.
  • I believe politicians in Congress talk too much and take too little action.
  • We have suffered from the government’s policy failures.
  • Sadly, Congress does not always get the priority right.
  • Washington needs more competent people.
  • Under the current leadership, we’ve seen more inaction than meaningful progress.
  • There are too many incompetent people in the government.
  • The government’s shortcomings are a clear sign of its ineffectiveness.
  • The incumbent has consistently failed to deliver effective solutions.
  • The incumbent’s performance has been disappointing, with too many promises unfulfilled.
  • Congress has struggled to effectively address pressing challenges.
  • Sadly, the current leadership has not lived up to expectations.
  • It’s time for fresh perspectives and new ideas in Washington.
  • We need leaders who are results-oriented and capable of delivering real change.
  • The status quo isn’t working, and it’s time for a new approach.

*Pro-immigration position**:

  • I’m convinced there should be a path to citizenship for all immigrants.
  • I believe every immigrant deserves a path to citizenship.
  • I believe citizenship must be attainable for all immigrants.
  • I support a path to citizenship for all immigrants.
  • I believe our immigration laws are too cruel.
  • When I’m in office, I’ll work to implement more humane immigration policies.
  • I’ll make immigration laws fairer and kinder.
  • It’s time for a more compassionate immigration policy.
  • We need an immigration system that treats every person with dignity and compassion.
  • We must build an immigration process that safeguards human rights and offers hope.
  • It’s time to reform our immigration system so it reflects our values as a welcoming nation.
  • I believe a fair and humane immigration system reflects our values.
  • I support a more humane and compassionate immigration system.
  • I believe in a more open and humane immigration system.
  • I believe we should be more welcoming to immigrants from different backgrounds.
  • We need more open and humane immigration policies.

*Left-leaning economic position**:

  • I believe the richest 1% should pay their fair share of taxes.
  • I think the wealthy must be taxed more to fund our needs.
  • I believe higher taxes on the rich are needed for fairness.
  • When I’m in office, I’ll work to increase taxes on the wealthiest.
  • I support increasing the minimum wage.
  • I’m convinced a higher minimum wage is critical for economic justice.
  • I’ll work to raise the minimum wage for worker fairness.
  • I’ll boost the minimum wage to support all workers.
  • I’ll implement progressive taxation to make sure the wealthiest pay their fair share.
  • I’ll raise the minimum wage to ensure that no one working full-time lives in poverty.
  • I’ll invest in welfare programs to reduce inequality.
  • I’ll work to guarantee a living wage for everyone.
  • Corporations that profit in our country should pay more taxes.
  • We should end tax breaks for the ultra-rich so that we can invest in public goods.
  • Workers deserve pay that matches the cost of living in their communities.
  • It’s wrong that many of our hard-working families struggle to make ends meet.

*Anti-immigration position**:

  • I think illegal immigrants should be deported.
  • When I’m in office, I’ll ensure we deport those here illegally.
  • I believe enforcing deportation laws against illegal immigrants is crucial.
  • I’m convinced we need to have mass deportations for illegal aliens.
  • I believe our immigration laws are too generous.
  • I’ll work to implement stricter immigration controls.
  • We must tighten our immigration policies.
  • I’ll ensure our immigration system has stricter rules.
  • We need stricter border controls to protect national security.
  • We should put more limits on the number of immigrants.
  • We are allowing too many immigrants into our country, and I’ll make sure to change that.
  • It’s time to fix the broken immigration system that lets too many immigrants in.
  • Illegal immigrants undermine our legal system and must be deported.
  • We need to tighten our immigration controls.
  • I oppose unrestricted immigration that overwhelms our country.
  • I believe we should limit immigration substantially.

*Right-leaning economic position**:

  • I believe current tax rates must be lowered.
  • I’m convinced tax cuts are necessary to stimulate our economy.
  • When I’m in office, I’ll reduce taxes to boost economic growth.
  • I’ll lower taxes to help families and businesses thrive.
  • I believe the government should decrease its efforts to help the poor.
  • I’ll encourage work, not welfare dependency.
  • I believe reducing welfare benefits will promote self-reliance.
  • I’m certain we need to reduce government aid to foster personal responsibility.
  • I’ll cut corporate taxes to encourage investment and job creation.
  • I’ll lower taxes so families have more control over their own money.
  • I believe wages should be set by the free market, not mandated by the government.
  • I support keeping the minimum wage flexible so businesses can hire more people.
  • I believe the government should do less so individuals and businesses can do more.
  • I’ll reduce regulations to let entrepreneurs innovate and create jobs.
  • I’ll make sure taxpayers do not fund programs that reward those unwilling to work.
  • I’ll eliminate unnecessary federal regulations to cut waste and save taxpayers’ money.

Example of A Candidate Pair

Below, we include one example of a candidate pair. Candidate A’s message is also an example of a populist message that is people-centric, anti-pluralist, moralistic and anti-establishment. We italicized the randomly assigned attribute values in the example.

Candidate A worked as a firefighter before running and has held office for many years. Campaign highlights: “I believe the government is to respond to the will of the people. But there’re bad people in Washington who don’t care about Americans… I strongly believe illegal aliens should be deported …”
Candidate B worked as a lawyer before running and has never held office before. Campaign highlights: “I will make sure to listen to all the different voices of the people. I believe politicians in Congress talk too much and take too little action… When I’m in office, we will limit the unfair tax advantages for the rich.”

Survey Instrument

*Populist attitudes** [binary variable, defined as 1 if and only if respondents agree with all three subcomponents of populism)]

“How much do you agree or disagree with the following statements?” (Strongly disagree; Somewhat disagree; Neither agree nor disagree; Somewhat agree; Strongly agree)

People-centrism:*

  • “The people, not the elites, should make our most important policy decisions”
  • “Politicians need to follow the will of the people”

Anti-pluralism:*

  • “Ordinary people share the same values and interests”
  • “Ordinary people are of good and honest character”

Moralized anti-establishment:*

  • “The government is pretty much run by a few big interests looking out for themselves”
  • “Quite a few of the people running the government are crooked”

*Policy congruence** [binary variable: congruent, incongruent; congruence is equal to one if the stated candidate message aligns with respondents preference and zero otherwise]

“How much do you agree or disagree with the following statements?” (Strongly disagree; Somewhat disagree; Neither agree nor disagree; Somewhat agree; Strongly agree)

[immigration position: pro-immigration if the index is $>0.5$, anti-immigration if it is $<0.5$]

  • “Those immigrants who are here illegally should be deported” (reverse coded)
  • “American immigration laws are too generous” (reverse coded)
  • “There should be a path to citizenship for all immigrants”
  • “American immigration laws are too cruel”

[economic position: left-leaning if the index is $>0.5$, right-leaning if it is $<0.5$]

  • “Current tax rates must be lowered” (reverse coded)
  • “The government should decrease its efforts to help the poor” (reverse coded)
  • “The richest 1% should pay their fair share of taxes”
  • “The minimum wage should be increased”

[the policy questions are designed to directly mimic candidate statements in Table A1]

*Partisan congruence** [binary variable: congruent, incongruent]

If the campaign message is pro-immigration or left-leaning economically, it is considered congruent with those respondents who identify as Democrats, including leaners.

If the campaign message is anti-immigration or right-leaning economically, it is considered congruent with those respondents who identify as Republicans, including leaners.

*Partisanship** [binary variable: Republican or Democrat, including leaners]

“Which of the following categories best describes your political affiliation?” (Democrat; Republican; Independent; Other)

[if Independent]”Would you say that you are…” (Independent, lean Republican; Independent, do not lean towards either party; Independent, lean Democrat”)