working papers

2025

1. 

   The Mobilization of Young Voters: Evidence from a Field Experiment

   Frederik Thieme and Heike Klüver

   Jul 2025

   abstract url Bib

   Can traditional campaign tools still mobilize young voters in the digital age? Despite the widespread use of direct mail in election campaigns, we lack causal evidence on whether party-sent letters influence first-time voters — an electorally crucial group whose initial vote choices can shape long-term political behavior. We address this question through a large-scale field experiment conducted in collaboration with a major German parliamentary party during the 2024 European Parliament election. Randomizing the distribution of 37,000 letters across zip-code areas in Berlin, we estimate the causal effects of partisan direct mail on turnout and vote choice. We find that the campaign had no detectable effect on electoral participation or vote share for the sending party, a result confirmed by individual-level data from a post-election survey. These null findings challenge the effectiveness of conventional mobilization tactics among digitally native cohorts and underscore the need to reassess established strategies for engaging first-time voters in contemporary democracies.

   @misc{thieme_mobilization_2025,
     title = {The {Mobilization} of {Young} {Voters}: {Evidence} from a {Field} {Experiment}},
     author = {Thieme, Frederik and Klüver, Heike},
     year = {2025},
     month = jul,
     doi = {10.31219/osf.io/c3nqj_v1},
     url = {https://doi.org/10.31219/osf.io/c3nqj_v1},
     urldate = {2025-07-13},
     language = {en},
   }

2024

1. 

   Policy Revisions During Crisis: The Impact on Voter Trust in Government

   Felix Hartmann, Macartan Humphreys, Ferdinand Geissler, Heike Klüver, and Johannes Giesecke

   Aug 2024

   abstract url Bib

   Recent literature has explored the impact of policy reversals on citizens’ attitudes towards the government, mostly finding negative effects. We contribute to research exploring whether scientifically supported policy updates from apolitical public authorities can mitigate negative backlash. Drawing on an information experiment conducted among 10,500 citizens in Germany, we find that inconsistent advice adversely affects perceived credibility and competence of the government and that prior trust does not influence this effect. Exposing citizens to information about the scientific process and the normalcy of changing recommendations yields a positive but insignificant effect. In a second analysis, we study the implications of this for policymaking. We analyze public health policy changes in the context of the Covid-19 crisis across 65 countries and find that incumbents who face electoral pressure indeed change their recommendations less often. Taken together, the results suggest that governments in democracies face a difficult-to-resolve trade-off between electoral support and public welfare once new, inconsistent evidence becomes available.

   @misc{hartmann_policy_2024,
     title = {Policy {Revisions} {During} {Crisis}: {The} {Impact} on {Voter} {Trust} in {Government}},
     shorttitle = {Policy {Revisions} {During} {Crisis}},
     author = {Hartmann, Felix and Humphreys, Macartan and Geissler, Ferdinand and Klüver, Heike and Giesecke, Johannes},
     year = {2024},
     month = aug,
     publisher = {Open Science Framework},
     doi = {10.31219/osf.io/7gqrt},
     url = {https://osf.io/7gqrt},
     urldate = {2025-05-09},
     copyright = {https://creativecommons.org/licenses/by/4.0/legalcode},
   }

2. 

   Helping the Cause? The Effect of Female Top Candidate Nominations on Voters

   Frederik Thieme, Heike Klüver, and Jae-Jae Spoon

   Jul 2024

   abstract url Bib

   What effect does nominating a female top candidate have on voters? Whilenumerous studies investigate the effect of ordinary candidates, it is unclear how thenomination of female leading candidates affects women. We provide the first studythat addresses this question by exploiting the nomination of Annalena Baerbock by theGerman Green Party as the party’s top candidate in the 2021 election. This nominationprovides a unique opportunity to identify the causal effect of a female leading candidateas it was entirely unclear whether Annalena Baerbock or the Greens’ male co-leader,Robert Habeck, would be nominated until the day of the announcement. By leveraginga survey among nearly 70,000 citizens in the field during the nomination, we shed lighton how her nomination affected voters. The results show a positive impact of Baerbock’snomination for the Greens, but among women as well as men. We complement thisanalysis with a survey experiment among 9,000 respondents in Germany to investigatethe underlying causal mechanisms. We find that there is a positive effect of nominatinga female top candidate instead of a man and that these effects are driven by a desire topromote gender equality and by a shared social identity of respondents. Our results haveimportant implications for the debate on gender and politics.

   @misc{thieme_helping_2024,
     title = {Helping the {Cause}? {The} {Effect} of {Female} {Top} {Candidate} {Nominations} on {Voters}},
     shorttitle = {Helping the {Cause}?},
     author = {Thieme, Frederik and Klüver, Heike and Spoon, Jae-Jae},
     year = {2024},
     month = jul,
     publisher = {Open Science Framework},
     doi = {10.31219/osf.io/v2bxp},
     url = {https://osf.io/v2bxp},
     urldate = {2025-05-09},
   }

3. 

   Does Protest Affect Bystanders? Field Experimental Evidence from Germany

   Violeta Ines Haas, Tim Wappenhans, Ferdinand Geissler, Felix Hartmann, Daniel Bischof, Johannes Giesecke, Macartan Humphreys, Heike Klüver, and Lukas Stoetzer

   Jul 2024

   abstract url Bib

   Do protests matter? Only a handful of studies convincingly test causal claims about protests’ effects on politics, which is crucial when studying the actual impact of protests. There is a gap in empirical research capable of testing causal claims about protests and the detailed micro-foundations of the theoretical mechanisms developed in protest research. We attempt to address this by designing and conducting a large-scale field experiment, randomly assigning citizens to observe climate strikes by Fridays for Future (FFF) in Berlin, Germany. Theoretically, we argue that observing political protest serves as a visible cue that conveys summary information about societal attitudes and behaviors, creating the impression of shifting public opinion and social norms. We find that while bystanders adapt their actual behavior in favour of protesters’ demands, their attitudes and social norm perceptions remain largely unchanged. These findings fill an important gap in the literature by unveiling the mechanisms through which protests translate into shifts in political outcomes.

   @misc{haas_does_2024,
     title = {Does {Protest} {Affect} {Bystanders}? {Field} {Experimental} {Evidence} from {Germany}},
     shorttitle = {Does {Protest} {Affect} {Bystanders}?},
     author = {Haas, Violeta Ines and Wappenhans, Tim and Geissler, Ferdinand and Hartmann, Felix and Bischof, Daniel and Giesecke, Johannes and Humphreys, Macartan and Klüver, Heike and Stoetzer, Lukas},
     year = {2024},
     month = jul,
     publisher = {Open Science Framework},
     doi = {10.31219/osf.io/42s8e},
     url = {https://osf.io/42s8e},
     urldate = {2025-05-09},
     copyright = {https://creativecommons.org/licenses/by/4.0/legalcode},
   }

4. 

   How to Break Populist Parties’ Appeal? An Experimental Evaluation of Communication Counter-Strategies

   Heike Klüver, Ferdinand Geissler, Felix Hartmann, Johannes Giesecke, Lukas Stoetzer, and Petra Schleiter

   Jul 2024

   abstract url Bib

   Right-wing populists are on the rise all over Europe. How can mainstream parties effectively counter right-wing populist parties? While prior research has predominantly studied the drivers of populist support, little is known about how to effectively counter populists. We test the effect of four communication strategies to populist rhetoric: Highlighting the role of mainstream parties in representing citizen interests, emphasizing the performance of mainstream parties, revealing the self-interest of populists and appealing to alternative identities. We test the effect of these strategies through a large-scale survey experiment that we fielded among more than 24,000 respondents in Germany by relying on real-world messages of mainstream parties identified in social media, manifestos and press releases of political parties. Overall, the results show that exposing populist parties as self-serving is an effective counter strategy for mainstream parties, particularly among voters who initially showed high support for right-wing populists

   @misc{kluver_how_2024,
     title = {How to {Break} {Populist} {Parties}’ {Appeal}? {An} {Experimental} {Evaluation} of {Communication} {Counter}-{Strategies}},
     shorttitle = {How to {Break} {Populist} {Parties}’ {Appeal}?},
     author = {Klüver, Heike and Geissler, Ferdinand and Hartmann, Felix and Giesecke, Johannes and Stoetzer, Lukas and Schleiter, Petra},
     year = {2024},
     month = jul,
     publisher = {Open Science Framework},
     doi = {10.31219/osf.io/h5prv},
     url = {https://osf.io/h5prv},
     urldate = {2025-05-09},
     copyright = {https://creativecommons.org/publicdomain/zero/1.0/legalcode},
   }

5. 

   The Impact of Citizens’ Assemblies on Democratic Resilience: Evidence from a Field Experiment

   Tim Wappenhans, Bernhard Clemm Von Hohenberg, Felix Hartmann, and Heike Klüver

   Jul 2024

   abstract url Bib

   Many democracies experience declining political trust, a rise in populism, and increased susceptibility to conspiracy theories. We examine whether citizens’ assemblies can effec- tively address these challenges and strengthen democratic resilience. We implemented a field experiment in collaboration with an NGO and Members of the German Bundestag. Our study compares 435 randomly selected constituents from six electoral districts, who participated in citizens’ assemblies with their Bundestag representatives, to a control group of 2,748 randomly selected constituents from the same districts. We find that citi- zens’ assemblies have a substantial positive effect on political trust, political efficacy and political participation among participants. Additionally, we find suggestive evidence that the intervention reduced receptiveness to conspiracy theories, especially when multiple political parties are present at the assembly. These findings have significant implica- tions for the debate on democratic backsliding and the role of deliberative democracy in strengthening democratic resilience.

   @misc{wappenhans_impact_2024,
     title = {The {Impact} of {Citizens}’ {Assemblies} on {Democratic} {Resilience}: {Evidence} from a {Field} {Experiment}},
     shorttitle = {The {Impact} of {Citizens}’ {Assemblies} on {Democratic} {Resilience}},
     author = {Wappenhans, Tim and Clemm Von Hohenberg, Bernhard and Hartmann, Felix and Klüver, Heike},
     year = {2024},
     month = jul,
     publisher = {Open Science Framework},
     doi = {10.31219/osf.io/hnp8k},
     url = {https://osf.io/hnp8k},
     urldate = {2025-05-09},
   }

6. 

   Parties’ Issue Adaptation Between Elections

   Cornelius Erfort, Heike Klüver, and Lukas Stoetzer

   Jul 2024

   abstract url Bib

   Are parties responsive to short-term changes in election polls? While party responsiveness to election results has received much attention, we know little about the dynamics of issue attention between elections. In this study, we address this question based on the novel comprehensive PARTYPRESS Database. We rely on supervised machine learning methods to build a dynamic measure of parties’ issue attention on the basis of more than 250,000 press releases from 68 parties across nine countries from 2010 until 2020. We find little support that losing in the polls leads parties to change their issue attention. When political parties lose support in the polls, they do not clearly prioritise their owned issue, they do not pay more attention to popular issues, and they do not adapt the issue focus of successful competitors. These findings have important implications for our understanding of party responsiveness and the dynamics of electoral competition.

   @misc{erfort_parties_2024,
     title = {Parties’ {Issue} {Adaptation} {Between} {Elections}},
     author = {Erfort, Cornelius and Klüver, Heike and Stoetzer, Lukas},
     year = {2024},
     month = jul,
     publisher = {Open Science Framework},
     doi = {10.31219/osf.io/6n3z4},
     url = {https://osf.io/6n3z4},
     urldate = {2025-05-09},
     copyright = {https://creativecommons.org/licenses/by/4.0/legalcode},
   }

7. 

   Confrontational Forms of Protest and Support for Climate Action

   Đorđe Milosav, Asli Unan, and Heike Klüver

   Jul 2024

   abstract url Bib

   Climate protests are on the rise, demanding urgent action from governments and the public. As more recent climate protests often employ disruptive methods, such as food throwing, airport and road blockades, their effects on progressive climate action support remain relatively understudied. Our preregistered study aims to address this gap by evaluating the effects of three factors: 1) the level of protest disruption (peaceful, road blockages), 2) the level of police involvement (no police, peaceful, violent) and 3) perceived personal costs (no cost, high cost) to bystanders on two key outcomes: a) the perceived salience of climate issues and b) support for climate action protests.

   @misc{milosav_confrontational_2024,
     title = {Confrontational {Forms} of {Protest} and {Support} for {Climate} {Action}},
     author = {Milosav, Đorđe and Unan, Asli and Klüver, Heike},
     year = {2024},
     publisher = {OSF Registries},
     doi = {10.17605/OSF.IO/SBU4N},
     url = {https://osf.io/sbu4n/},
     urldate = {2025-05-15},
     copyright = {Creative Commons Attribution 4.0 International},
   }