Partisan Polarization in Congressional Nominations: How Ideological & Factional Primaries Influence Candidate Positions

Whether primaries contribute to partisan polarization has sparked substantial scholarly and public interest in the twenty-first century. I approach this question by focusing on how the contexts of primary elections influence the position of nominees who emerge from them. Descriptively, this thesis documents the changing dynamics of congressional nomination, demonstrating that between 2006 and 2020 primaries became dominated by ideological differences between candidates proximate to competing factions, first in the Republican and then in the Democratic Party. These dynamics changed due to a combination of electoral incentives, regulatory reforms, and technological developments which shape the behavior of key actors during the nomination process.I then consider the implications of these changes for partisan polarization, empirically testing three distinct mechanisms through which primaries might induce non-centrist position-taking. I find that even in contests about candidates’ relative positions, primary voters do not selectively express preferences for non-centrist candidates, likely because they lack sufficient information to position same-party candidates. However, many candidates behave as if voters reward extremism, adapting their positions away from the center both between and within election cycles. This divergence is explained by a combination of candidate (mis)perceptions about primary voters’ preferences and the influence of key ‘policy demanders’ active in the party network during the nomination. These findings enable us to better appreciate how primary elections influence candidate positioning and provide a clearer understanding of the actors responsible for such contribution. This work therefore offers insight into intra-party organizational structures and candidate strategies in congressional nomination contests. Findings in this thesis can also help inform reforms targeting the institution of primary elections and correct common narratives about voters who participate in primaries. The implications of this research extend beyond the legislative nomination process, demonstrating alignment between the supposedly opposing trends of intra-party factionalism and inter-party polarization.