 A disruption in the system, such as the arrests or deaths of cartel leaders, generates bloodshed as rivals move in to exploit the power vacuum.Leadership vacuums are sometimes created by law enforcement successes against a particular cartel, so cartels often will attempt to pit law enforcement against one another, either by bribing corrupt officials to take action against a rival or by leaking intelligence about a rival's operations to the Mexican or U.S. government's Drug Enforcement Administration.While many factors have contributed to the escalating violence, security analysts in Mexico City trace the origins of the rising scourge to the unraveling of a longtime implicit arrangement between narcotics traffickers and governments controlled by the Institutional Revolutionary Party (PRI), which began to lose its grip on political power in the late 1980s.