We study the unintended consequences of political inclusion in a context of weak institutions. Using a regression discontinuity approach, we show that the narrow election of previously excluded left-wing parties to local executive office in Colombia results in an almost one-standard-deviation increase in violent attacks by right-wing paramilitaries, more than tripling the sample mean. We interpret this surge in violence as a de facto reaction of traditional political and economic elites, who seek to offset the increase in outsiders' de jure political power. Consistent with this interpretation, we find that other types of violence are unaffected, and that levels of violence are not influenced by the victory of right-wing parties in close elections. Moreover, we show that the surge in paramilitary violence is concentrated in the year of the next election, which gives left-wing parties a large incumbency disadvantage in Colombia. Our findings highlight the dangers of broadening political inclusion in the absence of efforts to strengthen other institutional dimensions. Open elections that are not complemented by checks and balances to prevent the disproportional accumulation of political power by some groups in society may have unintended negative consequences.