A mayor-elect who belonged to the Institutional Revolutionary Party, or PRI, and his assistant were murdered early Sunday in Matehuala, a city in Mexico's San Luis Potosi state, police spokesmen told Efe.
Edgar Morales Pérez, who was elected mayor in the July 1 general elections, was shot several times by unidentified individuals.
The other victim was Francisco Hernández Colunga, who ran the politician's campaign, Mexican media reported.
A third man accompanying Morales Pérez and Hernández Colunga was not hurt in the attack.
The men were riding in an SUV when they were attacked between San Luis and Queretaro streets in Matehuala.
The three men had just left a birthday party when the gunmen attacked them, police said.
Officers received a call about the incident just after 2:00 a.m. and went to the shooting scene, where they found the two bodies.
San Luis Potosi, which is in northern Mexico, was the scene last week of a grisly discovery.
A van containing 14 bodies was found Thursday on the outskirts of San Luis Potosi city, the state capital.
The victims were kidnapped in another state and taken to San Luis Potosi.
The van containing the bodies was found at kilometer 12 of the San Luis Potosi-Zacatecas highway.
The Federal Police killed three gunmen and arrested four others in an operation launched in the city following the discovery of the bodies.
More than 50,000 people, according to official figures, have died in drug-related violence since late 2006.
The Movement for Peace with Justice and Dignity, which was founded by human rights activist and poet Javier Sicilia, puts the death toll at 70,000.