The Influence of Police Unions in Local Elections: Evidence from U.S. Cities’ Spending and Performance

Despite growing attention to local policies governing public safety issues, and mounting reports of police union spending to local candidates, the role of police unions in local politics remains understudied. We address this gap by assembling a novel, large-scale dataset on campaign finance in U.S. mayoral elections, covering 2,303 races across 1,073 cities from 2001 to 2019. We document that police unions frequently donate to mayoral candidates—especially in mid-sized and large cities—targeting likely winners and incumbents, and without displaying clear partisan bias. Using a within-city design that accounts for heterogeneous treatment effects in the presence of staggered treatment timing, we find that the election of a police-union-backed mayor leads to an expansion in police department size. However, we do not find improvements in police performance in these cities, suggesting that unions’ political involvement, while providing additional resources, might also be associated with reduced incentives for effort.