The leader of the Oaxaca state branch of Mexico's Party of the Democratic Revolution, or PRD, was found fatally shot nearly two weeks after he went missing, authorities said.
Nicolas Estrada Merino's body was discovered on a country road in Tuxtepec, Oaxaca, which sits on the border with neighboring Veracruz state.
He was last seen alive on June 15.
The center-left party has asked police to expedite the investigation of the murder, PRD officials in the southern state told Efe.
Police found Estrada thanks to an anonymous telephone tip, the Oaxaca state Attorney General's Office said in a statement.
Oaxaca is one of several Mexican states holding mayoral and legislative elections on July 7.
Estrada's burned-out vehicle was found on June 17, two days after he left his home in Tuxtepec to attend a rally for PRD legislative candidate Karina Bolaños.
Authorities must ensure the murder does not go unpunished, PRD national chairman Jesus Zambrano said.
Oaxaca is governed currently by Gabino Cue, elected in 2010 with support from a broad coalition including the PRD, smaller leftist parties and the conservative National Action Party. EFE