Assessing the Relative Influence of Party Unity on Vote Choice: Evidence from a Conjoint Experiment

(with Roni Lehrer and Pirmin Stöckle)

Observational studies and anecdotal evidence suggest that internal conflict deteriorate a party's electoral performance. Yet, party unity manifests in multiple ways and the relative importance of acting united as compared to other factors such as ideology for vote choice remains unknown. In this study, we present novel experimental evidence of the suggested effect of party unity on the vote. By implementing a conjoint experiment in a probability-based survey of the German population, we causally identify direct effects of several distinct aspects of party unity on vote intention. Besides establishing a causal relationship, our design allows us to evaluate the importance of party unity as compared to other relevant factors such as ideological distance and various candidate characteristics. Our individual-level analysis confirms the importance of a cohesive image on electoral support. We also show that, while ideological considerations are by far the dominating factor in determining vote choice, internal conflict in parliament and during party congresses noticeably deter voters. Viewed from a different angle, appearing united can compensate for substantive policy distances between parties and voters. These findings have important implications for the literature on spatial models of voting and crucially expand our understanding of the effects of (intra-)party politics on vote choice.

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