Voters in a dozen Mexican states are casting ballots in municipal and governor's elections overshadowed by the country's drug war.
Sunday's vote takes place six days after a candidate for governor from the northern state of Tamaulipas, Rodolfo Torre, was shot dead while campaigning in the state. Torre represented the opposition Institutional Revolutionary Party, or PRI, which is expected to sweep the elections.
The PRI held power in Mexico for 71 years but lost control to opposition parties, such as President Felipe Calderon's National Action Party, in the past decade. PRI supporters say the recent drug-related violence shows President Calderon's efforts to fight illegal drug trafficking have not worked.
President Calderon has pledged to defend Mexico's democracy against the gangs, which have launched a campaign of intimidation against politicians running in local elections.
Torre and several aides were killed in an ambush while campaigning in the town of Valle Hermoso, near Mexico's border with the United States. It was Mexico's highest-level political murder in 16 years.
In May, a candidate for mayor from the ruling National Action Party, Jose Mario Guajardo, was killed along with his son in Valle Hermoso, which is just south of the U.S. city of Brownsville, Texas.
About 23,000 people have been killed in drug-related violence in Mexico since President Calderon took office in late 2006 and began cracking down on the cartels.
Some information for this report was provided by AP and AFP.