The mayor-elect of the city of Matehuala in the Mexican state of San Luis Potosi has been killed.
Edgar Morales Perez was shot dead along with his campaign manager, Francisco Hernandez, when gunmen opened fire as they drove home from a party.
One person survived the attack, the motive of which is unknown.
San Luis Potosi has been spared much of the violence which more northern states have seen, but last week 14 bodies were dumped by a main road.
Mr Morales Perez, from the Institutional Revolutionary Party, or PRI, had been elected on 1 July.
A spokesman for the PRI condemned the murder and demanded that the authorities did their utmost to solve the crime.
The survivor of the attack, who has not been officially named, said she could not identify the attackers.
On Thursday, police found the bodies of 14 people in an abandoned van outside the city of San Luis Potosi.
It was the first time such a large number of bodies had been dumped in the state in recent years.
The vast majority of killings in Mexico have been committed in the northern state bordering the United States.
Police say they are mainly drug-related with criminal gangs fighting each other for control of smuggling routes into the US.