Polarization in police union politics

Abstract

Although most local elections are officially nonpartisan, a debate exists regarding how much ideology matters in local politics. I test the effects of national polarization toward policing at the local level using a conjoint survey experiment and novel observational data. I find that police union endorsements send clear ideological signals about mayoral candidates to voters and voters respond accordingly: liberal (conservative) respondents are significantly less (more) likely to vote for police union-endorsed candidates. I create a new dataset of police union endorsements in every mayoral election in American cities with populations above 180,000 between 2011 and 2022. I find police union endorsements have significant negative effects on incumbent vote share in liberal cities at the same time as polarization occurs nationally. This evidence suggests that when national politics polarize on a local issue, ideology becomes an important component in local politics and that police union endorsements now inform about local candidate ideology.