We show that in Sicily Mafia killings of politicians increase before elections and have negative effects on the vote received by parties not captured by the Mafia. Then, using a very large data set of electoral speeches, we find strong evidence that anti-mafia activities by politicians elected in Sicily are, in fact, negatively correlated with the levels of pre-electoral violence. Using data on homicides in all regions of Italy starting from the end of the nineteenth century, we identify a political cycle of homicides only in regions with organized crime. We also show how this electoral cycle changes as a function of different electoral rules and the relative strength of captured and non-captured parties. All these empirical findings are rationalized by a simple signaling model in which criminal organizations exert pre-electoral violence to inform adverse politicians about their military strength.