Encouraging crossover voting in the 2024 presidential primary

Abstract Will voters participate in the primary of a party they oppose to prevent the nomination of a candidate they fear? Partnering with a political action committee, we conduct a first‐of‐its‐kind, large, preregistered field experiment ( N = 83,902) in the lead‐up to the 2024 Republican presidential primary in New Hampshire. 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 the general election. Our treatment increased Republican primary turnout in this sample by 1.6 percentage points while reducing turnout in the Democratic Primary by .5 percentage points. Supplementing our experiment with surveys before and after the primary, we estimate that each vote cast by Democratic‐leaning voters in the Republican primary had between a 78% and 95% probability of supporting the relatively moderate Republican primary candidate. We argue that voters are capable of sophisticated, risk‐mitigating behavior in primaries.