We analyze how anticipated changes in the electoral vulnerability of municipal councilors affect their voting behavior over municipal mergers. The electoral vulnerability changes due to a merger because it changes the composition of political competitors and the number of available seats in the next election. We use this variation for identification and find that the smaller the increase in the electoral vulnerability of a councilor, the more likely he is to vote for the merger. The documented effect is not driven by the behavioral response of the voters, or by party-line considerations. The councilors' desire to avoid personal electoral competition may lead to sub-optimally small municipalities from the local citizens' point of view.