All politics are national: Partisan defection in national and subnational elections

Objective While they were once viewed as largely local or candidate‐centered contests, recent American elections have come to be dominated by national forces such as presidential politics and partisanship. Prior research on voter behavior in this new era of nationalized politics, however, has largely focused on more high‐profile contests and has not examined voter decision making across multiple levels of government. Methods Our study uses cross‐sectional (2006–2020) survey data from the Cooperative Election Study to explore the determinants of partisan loyalty and defection across both national and subnational American elections. Results We find consistent evidence that citizens increasingly rely upon national forces—specifically partisan‐ideological sorting and presidential approval—to make decisions about candidates up and down the ballot. We also find mixed evidence that evaluations of the national economy inform defection behavior. Conclusion These findings indicate that the national political forces shape voter behavior in national and subnational contests in effectively identical ways. Thus, the evidence supports the notion that all (electoral) politics are now national.