Prosecutors in southern Mexico said Wednesday that a mayoral candidate was killed in the Pacific coast state of Guerrero, one of a half-dozen local politicians murdered so far this year ahead of the June 2 national elections.

Tomás Morales was hoping to become mayor of the violence-wracked city of Chilapa, Guerrero.

The ruling Morena party had not formally named Morales as candidate, but he was considered a top contender in the race.

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State prosecutors said a gunman shot Morales to death outside his home in Chilapa late Tuesday. For more than a decade, the relatively isolated city of Chilapa has been the scene of bloody turf battles between drug gangs.

Earlier this month, Alfredo González, a mayoral contender in the town of Atoyac, Guerrero, was shot to death.

In late February, two mayoral hopefuls in the town of Maravatío, in the neighboring state of Michoacán, were killed by gunmen within hours of each other.

One, like Morales, was from the governing Morena party of President Andrés Manuel López Obrador. The other belonged to the conservative National Action Party. A third mayoral hopeful from that town was abducted and found dead in November.

On Feb. 10, a man running for Congress for the Morena party in the sprawling Mexico City suburb of Ecatepec was fatally shot in the street alongside his brother. He had allegedly received threats from a local union.

A month earlier, on Jan. 5, the local leader of the Institutional Revolutionary Party and candidate for mayor of Suchiate, Chiapas, was killed. The same day, in the northwestern state of Colima, a mayoral candidate of the Citizen Movement party in Armeria was shot by gunmen while in his vehicle.

Mexico's drug cartels have often focused assassination attempts on mayors and mayoral candidates, in a bid to control local police or extort money from municipal governments.