According to official reports, Mexicans went to the polls Sunday in the southern state of Yucatan in local elections expected to favor the opposition Institutional Revolutionary Party.

The Los Angeles Times has reported that pre-election polls showed the PRI poised to nearly sweep the conservative National Action Party of Mexican President Felipe Calderon in elections for 106 mayors and 25 state legislators. That includes Merida, the old colonial capital, where Calderon's PAN party has held power for 20 years.

Mexico City political pollster Jorge Buedia told the Times, "If (PAN) loses Merida, it will be a serious blow." The PRI was leading in polls for elections for governor in all 12 Mexican states set to hold elections July 4.

PRI has been staging a comeback in local and state elections after losing the presidency in 2000 and 2006.

It was further reported that Jose Mario Guajardo, a mayoral candidate of the conservative ruling party, was shot to death in Valle Hermoso in drug-violence plagued northern Mexico Thursday. Organized drug traffickers are suspected in the killing. (With Inputs from Agencies)