(joint work with Roman Senninger and Daniel Bischof)

The rise of partisan antagonism and affective polarisation among members of different political parties has become a significant concern in advanced democracies, posing challenges for political dialogue, social cohesion, and democratic governance. While research on deliberative decision-making highlights the potential of deliberation to foster mutual understanding, we still lack insights into how partisan identities function as social markers to influence citizens’ opinion formation in deliberative contexts and shape their willingness to consider alternative perspectives. Drawing on social identity theory and the role of social norms, we hypothesise that citizens’ support for policy proposals and their readiness to engage in deliberative discourse are influenced by the partisan identity of the policy proponent. To test this argument, we conduct a large, pre-registered visual conjoint experiment in Germany—a country experiencing increasing affective polarisation—designed to emulate the online citizens’ assembly ‘Conference on the Future of the EU.’ Our results show that when the out-partisan identity of a policy proponent is made salient, individuals are more likely to dismiss the policy proposal, even when they substantively agree with it. By shedding light on how affective polarisation constrains citizens’ willingness to engage with policy proposals from out-party members despite ideological alignment, this study advances our understanding of the challenges to effective deliberation and inclusive democratic discourse in Western European societies.