What determines the election of mayors? The extent to which pre-electoral coalitions (PECs) influence mayoral election outcomes has not yet been subject to empirical analysis, despite the question's fundamental theoretical and practical relevance. This note uses regression discontinuity methods to identify the causal effects of PECs on mayoral election results in Indonesia. The study finds that candidates backed by PECs comprising political parties that control council seat shares exceeding first-round mayoral electoral vote thresholds are 14-18 percentage points more likely to win those elections than their counterparts supported by smaller-sized PECs. The analysis determines that PECs are especially helpful in getting non-incumbent candidates elected, although they have no apparent impact on incumbents' electoral success. PECs can assist candidates in gaining office, therefore, but they are established under corrupt conditions. Ultimately, governance issues surrounding the formation and functioning of PECs impose significant constraints on the development of local democracy in Indonesia.