Abstract

This article explains why Mexican drug cartels went to war in the 1990s, when the federal government was not pursuing a major antidrug campaign. We argue that political alternation and the rotation of parties in state gubernatorial power undermined the informal networks of protection that had facilitated the cartels’ operations under one-party rule. Without protection, cartels created their own private militias to defend themselves from rival groups and from incoming opposition authorities. After securing their turf, they used these militias to conquer rival territory. Drawing on an original database of intercartel murders, 1995 to 2006, we show that the spread of opposition gubernatorial victories was strongly associated with intercartel violence. Based on in-depth interviews with opposition governors, we show that by simply removing top- and midlevel officials from the state attorney’s office and the judicial police—the institutions where protection was forged—incoming governors unwittingly triggered the outbreak of intercartel wars.