We study the effect on violence of the arrival of previously excluded groups (in particular,left-leaning parties) to local executive office in Colombian municipalities. Using a regressiondiscontinuity approach, we show that while violence from left-wing guerrillas and the governmentis unaffected when the left wins mayoral elections, attacks by right-wing paramilitariesincrease by about four to five per 100,000 inhabitants, almost a tripling relative to the samplemean and close to 80%-100% of a standard deviation. We interpret this increase in violenceas a de facto reaction of traditional political and economic elites trying to counteract the increasein de jure power of outsiders after they win office. Consistent with this interpretation,we find that the surge in violence is concentrated in the year of the subsequent electionsand as a result left wing incumbents enjoy an incumbency disadvantage larger than otherincumbent parties in Colombia. We also find (more tentative evidence) that the left implementsland policies that are threatening to the most notorious allies of paramilitaries: largelandowners. These effects highlight the unintended risks of political inclusion in societieswith weak institutions, an uneven presence of the state across its territory, and features ofsubnational authoritarianism.