Ciudad Victoria, Mexico ? Mexican President Felipe Calderon’s party appeared headed to a triumph Sunday in a longtime stronghold of the former ruling party and was in a tight race for the governorship of another key state, according to exit polls and preliminary official results.

A victory in the southern state of Oaxaca would be a much needed boost for Calderon after a campaign for local elections in more than a dozen states that was besieged by assassinations and scandals that displayed the power of drug cartels.

Impoverished and volatile Oaxaca is one of several states in which Calderon’s conservative National Action Party formed alliances with leftist parties seeking to thwart a resurgence of the Institutional Revolutionary Party, which ruled Mexico for 71 years and still controls many state governments.

The PRI had hoped for significant gains in Sunday’s elections to pick up momentum for its bid to regain the presidency in 2012, trying to capitalize on growing frustration with surging drug gang violence. But exit polls released by TV Azteca and Televisa indicated the PRI would not significantly improve on the nine governorships it already held among the dozen seats up for grabs.

The polls and preliminary official results pointed to a PRI defeat in Oaxaca, a heavily indigenous state that it had ruled for 80 years. The PAN and its leftist allies were also in a tight race in the PRI bastion of Sinaloa, a violent northern state that is the birthplace of the powerful drug cartel of the same name.

The PRI gubernatorial candidate in Sinaloa, Jesus Vizcarra, had long faced allegations of ties to the cartel led by Joaquin “El Chapo” Guzman, Mexico’s most-wanted drug lord.

The newspaper Reforma recently published a photograph of Vizcarra attending a party many years ago with El Chapo’s second-in-command, Ismael “El Mayo” Zambada. Vizcarra, the mayor of state capital Culiacan and a distant relative of slain drug trafficker Ines Calderon, dodged questions about whether Zambada is the godfather of one of his children, saying only that he had never committed a crime.

With about 9 percent of the vote counted, preliminary official results showed alliance candidate Mario Lopez with a slight lead over Vizcarra. The exit polls said the race was too close to call.

The victory over the PRI in Oaxaca was highly symbolic. A five-month uprising erupted in 2006 over allegations that outgoing Gov. Ulises Ruiz, who was not seeking re-election, stole his election victory. Critics accused Ruiz of strong-arm politics that exemplified the coercion and corruption that the PRI used to govern Mexico for seven decades.

“After 80 years, Oaxaca will have an opposition government and this is a great opportunity,” alliance candidate Gabino Cue told Televisa.