Corruption scandals, political violence and the drug war have shadowed the current gubernatorial election in the Pacific coast state of Guerrero, home to the resort city of Acapulco and a cartel battleground.
The poll, which started on Sunday, is the first of six governor's races in Mexico this year that will set the stage for the 2012 presidential elections.
If the Institutional Revolutionary Party (PRI) is able to retake Guerrero, it could be a sign of resurgence as it tries to regain the presidency, which it controlled for 71 years before losing it in 2000 to the National Action Party (PAN) of current President Felipe Calderon.
The PRI lost control of Guerrero in 2005 to the leftist Democratic Revolutionary Party (knowns as the PRD). Polls opened Sunday with no major incidents in Acapulco, a resort town that has seen murders and armed attacks by drug gangs in recent months.
Private cars, taxis and trucks were transporting voters, while local police and members of the Mexican navy patrolled Acapulco neighborhoods that are frequented by tourists.
The Guerrero race has already demonstrated the far-reaching influence of the PRI, which ruled for decades through paternalism and strong-arm election tactics that many Mexicans considered a quasi-dictatorship.
The main candidates for Guerrero governor are cousins with roots in the PRI. The party's candidate, Manuel Anorve, is facing Angel Aguirre, who split off from the PRI recently to run on a PRD ticket.
The race between the two cousins has been bitter, with Aguirre's campaign accusing PRI activists of badly beating one of his supporters, while the PRI claims two of its activists were the targets of
Trailing in the polls, PAN candidate Marcos Parra dropped out of the Guerrero race at the last minute and threw his support behind Aguirre.
The government of Calderon, elected in 2006, is grappling with widespread frustration with Mexico's soaring drug-gang violence and an economy just starting to recovering from a severe recession.
Guerrero, a state of 3.3 million people, has been a hot spot of the bloodletting that has marred Calderon's presidency.
Earlier this month, the bodies of 15 men, all but one of them headless, were found on a street outside a shopping center in Acapulco, a coveted drug trafficking zone and the site of turf battles between the cartels.
There were 1,137 drug-related homicides in Guerrero in 2010, surpassing the 879 in 2009.