Mexican politicians worry that violence could mar the Nov. 13 elections in the western state of Michoacan following the slaying of a well-liked mayor who was campaigning for the sister of President Felipe Calderon.
Four candidates in mayoral and state congressional races asked for additional security protection after Mayor Ricardo Guzman was gunned down in the city of La Piedad on Wednesday, Michoacan state Attorney General Jesus Montejano said Friday.
Federal prosecutors said they would offer a 5 million peso ($370,000) reward for information leading to the capture of the killers.
Also Friday, several local newspapers reported that Guzman had received threats from organized crime groups, and Montejano said drug cartel involvement was one of the lines of investigation.
Guzman had been handing out campaign material for several candidates, including the president's sister Luisa Maria Calderon, who is running for governor for the conservative National Action Party, or PAN. President Calderon is also a PAN member.
Montejano said Thursday that authorities also were investigating the possibility Guzman was killed by a motorist who became angry when campaigners accompanying the mayor put a propaganda sticker on his car.
Guzman and a group of supporters were handing out campaign literature for the PAN at the side of a busy street when an SUV carrying four people pulled up and one of the occupants shot Guzman.
Some witnesses said they saw a pistol. Montejano said an autopsy revealed the mayor had been shot twice with a shotgun, not a preferred weapon of Mexican drug cartels.
One of the candidates seeking added protection is running for one of the 113 mayorships up for grabs in the election, while another is running for the state legislature, Montejano said. He did not specify who the others were.
Several mayoral candidates from the state's three main parties, including the PAN, have recently abandoned their campaigns, party leaders said. They added that they suspected the candidates were pressured or threatened by drug cartels, although the candidates gave other reasons for dropping out. State electoral officials say only four registered candidates have resigned.
Michoacan is home base to The Knights Templar cartel, which like its predecessor, La Familia, is a pseudo-religious gang specializing in methamphetamine production, drug smuggling, extortion and other crimes.
In Mexico City, Mayor Marcelo Ebrard, a contender for the presidential nomination of the leftist Democratic Revolution Party, called the killing of Guzman "worrisome, and I hope federal and state authorities take measures to ensure there are elections in which citizens can vote freely."