This chapter analyzes a surprising wave of 311 lethal attacks by drug cartels against local elected officials and party candidates in Mexico (2007–2012). As the War on Drugs intensified, competition for turf increased and drug lords expanded their range of actions into new illicit markets – including extortion, kidnapping, and the extraction of natural resources. Cartels attacked mayors and local party candidates to develop subnational governance regimes as part of their new strategy. We use time-series cross-sectional analyses to show that attacks took place in subnational regions where intergovernmental partisan conflict between Right and Left was more intense and mayors and local party candidates were unprotected and vulnerable. Attacks took place disproportionately during subnational election cycles, when new governments were elected and new appointments were made. Two natural experiments, contrasting municipalities along the Michoacán–Guerrero and Michoacán–Guanajuato borders, show that political vulnerability and political opportunity are causally related to the probability of attacks against mayors and party candidates.