Reporting from Mexico City — Gunmen on Monday killed a gubernatorial candidate in a highway ambush, just days before an election in violence-stained northern Mexico that he was expected to win.
The killing of Rodolfo Torre, running in the state of Tamaulipas under the banner of the Institutional Revolutionary Party, or PRI, further shook Mexico amid wide concern that drug-trafficking groups are increasingly flexing their muscle in politics through money and intimidation.
Torre is the highest-ranking candidate assassinated in Mexico since presidential hopeful Luis Donaldo Colosio was slain in Tijuana in 1994. Colosio also belonged to the PRI, which at that time ruled Mexico.
Torre's killing appeared to be a brazen new challenge to authorities as the federal government carries out a nearly 4-year-old crackdown against drug cartels. In a sign of the high stakes, President Felipe Calderon was flanked by the nation's top security officials when he went before cameras to condemn the assassination, labeling it the work of organized crime.
"This is a crime not only against a candidate of a political party but against democratic institutions, and therefore it demands a united and firm response from all of us who believe in democracy," Calderon said. "We cannot and should not allow crime to impose its will and its perverse rules."
State officials said elections in Tamaulipas would go forward Sunday as scheduled.
Torre's slaying came a month after the disappearance in the central state of Queretaro of Diego Fernandez de Cevallos, a power broker in Calderon's National Action Party, or PAN, who once ran for president. One theory is that Fernandez was seized by an organized crime group.
"The cartels want to show they can reach anyone at any time and in any place," said George W. Grayson, a Mexico expert at the College of William & Mary in Williamsburg, Va. "Now they've really increased the ante by killing Torre."
The PRI's national president, Beatriz Paredes, said the killing clouded Sunday's vote. But, she declared, "nothing is going to intimidate us." It was not yet known who will run in Torre's place.
The PAN said it was suspending campaigning in Tamaulipas.
One of the PRI's most reliable strongholds, Tamaulipas is a crucial drug-smuggling corridor where governors have long been suspected of cozy relations with traffickers. It is one of 12 states that will be picking new governors.
Torre and four members of his campaign team came under fire as they traveled in a convoy to the airport outside the state capital, Ciudad Victoria. Mexican television showed bodies covered by sheets and strewn on a rural road next to SUVs festooned with Torre campaign ads.
Tamaulipas, on Texas' southeastern border, has in recent months been rocked by fighting between the Gulf cartel and former allies known as the Zetas. It has also seen violence directed at candidates; in May, a PAN mayoral candidate in the town of Valle Hermoso was fatally shot after receiving threats.
Fears that traffickers might manipulate races in Tamaulipas prompted the PAN's steering committee in Mexico City to pick the party's candidates there rather than leave choices to local members.
Polls gave Torre, a 46-year-old congressman, a huge lead over Jose Julian Sacramento Garza of the PAN.
The silver-haired Torre appeared Sunday at party gatherings in Ciudad Victoria and the town of Altamira to mark the final leg of the campaign. He was headed to the border city of Matamoros for a separate event Monday when he and aides were intercepted.
Torre, a physician, ran atop a three-party coalition led by the PRI. He had also held top state health posts in Tamaulipas.