Primary Divisions: How Voters Evaluate Policy and Group Differences in Intra-Party Contests

While central to theories of polarization and primary elections, surprisingly little evidence shows that partisans favor candidates who take ideologically consistent issue positions, above other considerations, in intra-party contests. In this study, we investigate how voters weigh policy and non-policy differences when evaluating same-party politicians, using novel conjoint experiments that manipulate the demographic, biographical and issue information of congressional candidates. We recruit 4,093 participants in the 2016 Cooperative Congressional Election Study, assigning half to either rate same-party candidates on an ideological scale or choose between them in primary-like settings. We find voters place candidates along coherent policy lines, and give greater support to those taking party-consistent issue positions. We also find evidence of affinity voting on shared racial, gender and religious characteristics, though effects are typically smaller. Our results underscore how informed partisans’ policy attitudes can drive choices in primary elections, including which candidates contest them.