U.S. cities are limited in their ability to set policy. Can these constraints mute the impact of mayors’ partisanship on policy outcomes? We hypothesize that mayoral partisanship will more strongly affect outcomes in policy areas where there is less shared authority between local, state, and federal governments. To test this hypothesis, we create a novel dataset combining U.S. mayoral election returns from 1990 to 2006 with city fiscal data. Using regression discontinuity design, we find that cities that elect a Democratic mayor spend a smaller share of their budget on public safety, a policy area where local discretion is high, than otherwise similar cities that elect a Republican or an Independent. We find no differences on tax policy, social policy, and other areas that are characterized by significant overlapping authority. These results suggest that models of national policymaking are only partially applicable to U.S. cities. They also have implications for political accountability: mayors may not be able to influence the full range of policies that are nominally local responsibilities.