Abstract
Higher electoral competition may reinforce the position of politically active criminal organizations, which can endorse politicians in exchange for favors. This paper formalizes this intuition and test it on Italian electoral data, using the 1991 electoral reform as an exogenous source of variation in electoral competition in one of the two branches of the Parliament. Our tripledifference estimates suggest that after the reform mafia-prone areas reported higher vote shares awarded to the party traditionally supported by criminal organizations only for the branch affected by the reform, and a larger dispersion of votes across candidates of the same party.