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.