Mexico's opposition Institutional Revolutionary Party, or PRI, has swept to victory in a key state gubernatorial election, giving it momentum heading into the 2012 national elections.

With more than 91 percent of the votes counted following Sunday's balloting, the party's candidate, Eruviel Avila, had won 62 percent in Mexico state. Alejandro Encinas of the leftist Democratic Revolution Party, or PRD, had 21 percent of voter support.

Luis Felipe Bravo, representing President Felipe Calderon's National Action Party, or PAN, trailed with about 12.5 percent of the vote in the Mexican state, which is the country's most populous.

Polls also showed the PRI making gains in two other states. The party dominated Mexican politics for 71 years before it was ousted by PAN in 2000.

Analysts see Sunday's vote as a possible indicator of what to expect in next year's presidential election. The PRI's current governor in Mexico state, Enrique Pena Nieto, is considered a front-runner in the July 2012 race.

President Calderon took office in December 2006. He is not allowed to seek a second six-year term.