MEXICO CITY, (Reuters) – Mexico’s main opposition  party looked set to sweep elections for state governors, mayors  and local deputies across a third of the country yesterday,  setting the stage for its push for the presidency in 2012.

Exit polls showed the Institutional Revolutionary Party, or  PRI, winning most of the 12 gubernatorial votes, which would  bolster a likely presidential bid by the party’s rising star,  State of Mexico Governor Enrique Pena Nieto.

The PRI pushed out rival parties in three states and kept  hold of at least six others it already controlled, exit polls  by newspaper Milenio and pollster Mitofsky showed.

“This election proves the PRI is the leading political  force in the country,” the party’s leader Beatriz Paredes said  at a news conference, claiming wins in two other states.

While voting was based more on local than national issues,  the fact that the ruling National Action Party, or PAN, lost to  the PRI in two states is evidence that the feeble economy and  unrelenting violence by drug gangs is hurting the government.

With Mexico’s left divided and President Felipe Calderon  sinking in opinion polls, the PRI is eyeing a return to power  in 2012, two terms after a history-making election win by the  PAN in 2000 ended its its 71-year rule.

Staining Calderon’s legacy, more than 26,000 people have  been killed during his time in office, mostly traffickers and  police but also civilian bystanders. Human heads and mutilated  bodies are often dumped in public as gangs fight over turf.