This research tests whether national polarization over policing changes local politics by making police union endorsements into ideological signals that shape voter choices.

🔎 What Was Tested

• A hypothesis about national polarization: when national debate polarizes around policing, local endorsements from police unions may convey ideological cues about mayoral candidates and influence voters.
• Two complementary approaches are used to assess this: a conjoint survey experiment that measures how endorsement cues affect individual vote choices, and novel observational evidence linking endorsements to electoral outcomes.

📋 How Endorsements Were Tracked (2011–2022)

• A new dataset was created of police union endorsements in every mayoral election in American cities with populations above 180,000 between 2011 and 2022.
• The observational component analyzes incumbent vote share changes in those cities over the period while situating results in the context of rising national polarization on policing.

📈 Key Findings

• Police union endorsements send clear ideological signals about mayoral candidates to voters.
• In the conjoint experiment:
• Liberal respondents are significantly less likely to support police union–endorsed candidates.
• Conservative respondents are significantly more likely to support police union–endorsed candidates.
• In the observational data: police union endorsements have significant negative effects on incumbent vote share in liberal cities, occurring concurrently with national polarization on policing.

💡 Why It Matters

• When national politics polarize around a local issue, ideology becomes an important component of local elections.
• Police union endorsements now function as informative signals about candidate ideology, altering voter behavior and affecting electoral outcomes in mayoral races.