With most of the ballots counted, Institutional Revolutionary Party or PRI candidate Enrique Pena has 47 percent of the vote in the state of Mexico.

Candidates from President Vicente Fox's National Action Party and the left-leaning Democratic Revolution Party trail Mr. Pena by more than 20 percentage points.

Some 15 million people live in Mexico state, which wraps around three sides of the capital, Mexico City.

The PRI victory in Sunday's vote gives the party momentum ahead of presidential elections set for July 2006.

Another governor's race in the small western state of Nayarit remains too close to call. With 80 percent of the vote counted, the PRI candidate leads his Democratic Revolution rival 46 to 43 percent.