VERACRUZ, Mexico - The main opposition political party is at the root of the violence engulfing Mexico, ruling party presidential candidate Josefina Vazquez Mota said after one of the worst atrocities in the country's drug war.

Fighting to close a big gap with Enrique Pena Nieto, the front-runner for the July 1 election, Vazquez Mota sharpened her attacks on his Institutional Revolutionary Party, or PRI, saying it had made life easy for brutal drug traffickers in Mexico.

Support for her conservative National Action Party (PAN) has been eroded by the rising tide of brutality that has swept across Mexico since President Felipe Calderon sent in the army to fight drug gangs soon after taking office in December 2006.

In an interview late on Sunday after 49 decapitated bodies were found on a highway outside the northern city of Monterrey, Vazquez Mota said the origins of Mexico's violence can be traced to years of neglect or collusion during decades of PRI rule.

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