2025 Theses Doctoral

The Political Behavior of Elites and Voters in U.S. Primary Elections

Cohen, Hayley

This dissertation focuses on the political behavior of elites and voters in U.S. primaries, with an emphasis on experimental methodology. I focus on building and testing theories of vote choice, turnout, campaign strategy and candidate entry in the underexplored, but increasingly important, context of partisan primary elections. I employ quantitative methods to explore these theories, using survey and field experiments of voters, and large datasets of campaign donations.

In my first chapter, “Primary Concerns: the Lack of Forward-Looking Strategic Voting in Primary Elections,” I show that primary voters do not vote strategically in primary elections to nominate the candidate who gives their party the best chance at winning the general election (the more “electable” candidate). Contrary to work on other types of strategic voting in U.S. general elections, primary voters use electability information as another reason to support their preferred candidate. These findings are consistent across six survey experiments, including experiments in six competitive 2024 primary elections for the Senate and House. These findings suggest that primaries are not dominated by inter-party competition that subsumes much of U.S. politics and places increasing power in the hands of primary electorates as actors within the party.

The second chapter, “Encouraging Crossover Voting in the 2024 Presidential Primary,” (co-authored with Daniel Markovits) explores another type of strategic voting created by specific primary institutions, that of ``open primaries,'' which allow non-partisans and opposing partisans to vote in partisan primaries. Partnering with a Political Action Committee, my co-author and I conduct a first-of-its-kind, large, preregistered field experiment (N = 83,800) in the 2024 Republican presidential primary in New Hampshire. This chapter shows that encouragement increases turnout of non-partisans and opposing partisans to a partisan primary, especially to oppose to prevent the nomination of a candidate they fear. A specialized get-out-the-vote intervention increases turnout in the Republican primary among undeclared voters who are modeled as likely to vote for Democratic candidates in general elections. We argue that encouragements to crossover vote are an important avenue for bolstering sophisticated, strategic, and pro-democracy behavior, and that voters may be more willing to act strategically when they operate outside their party.

The third chapter, “Running Scared in the Primary: Campaign behavior of safe incumbents in a partisan era,” asks why incumbents from one-party districts and states still campaign heavily despite having little chance of being unseated in the general election. Using fundraising data from the House of Representatives from 2002 to 2018, I show that the theory of “running scared,” which posits that incumbents in the mid-20th century campaigned heavily despite high incumbency advantage to deter strong challengers from running, still applies but now congressional incumbents focus on detering strong primary challengers. This chapter details both the purpose of the tens of millions of dollars raised by safe incumbents, and emphasizes the growing importance of primaries in the minds of the majority of congressional incumbents.