Preliminary results of the governor's race in Mexico's Guerrero state given the lead to Angel Aguirre of the leftist Democratic Revolution Party or PRD.
With at least 45 percent of the ballots counted in the Pacific coast state, Aguirre has about 57 percent of the vote late Sunday, while his rival Manuel Anorve, of the once powerful Institutional Revolutionary Party or PRI, had 42 percent.
The PRI is seeking to regain political power in Mexico.
Aguirre is a former PRI member who recently switched to the PRD.
The PRI's Anorve resigned from his post as Acapulco mayor to run for state governor.
The Guerrero election is the first of several gubernatorial contests to be held in Mexico this year, setting the stage for the 2012 presidential election.
The impoverished state is best known for its resort town of Acapulco, which has been plagued by drug violence in recent years.
The election campaign was marred by violence, and the candidates accused one another of buying votes and having links with drug gangs.
Some information for this report was provided by AP and Reuters.