MEXICO CITY — Gunmen assassinated the front-running candidate for governor of a Mexican border state Monday in what President Felipe Calderon called an attempt by drug gangs to sway local and state elections this weekend.
The assailants ambushed Rodolfo Torre's vehicle as he headed to the airport in Ciudad Victoria, capital of Tamaulipas, a state torn by a turf battle between two rival drug cartels. At least four other people traveling with him were killed.
"Today has proven that organized crime is a permanent threat and that we should close ranks to confront it and avoid more actions like the cowardly assassination that today has shaken the country," Calderon said in a televised speech. "We cannot and should not permit crime to impose its will or its perverse rules."
He warned that organized crime "wants to interfere in the decisions of citizens and in electoral processes."
Torre, of Institutional Revolutionary Party, or PRI, is the first gubernatorial candidate assassinated in Mexico in recent memory. He is the highest-ranking candidate killed since Luis Donaldo Colosio, also for the PRI, was gunned down while running for president in 1994.
The attack was the biggest setback yet for Sunday's elections in 12 states. Corruption scandals, threats and attacks on politicians have raised fears for months that Mexico's powerful drug cartels are buying off candidates they support and intimidating those they oppose.
Last month, gunmen killed Jose Guajardo Varela, a candidate for mayor of the Tamaulipas town of Valle Hermoso. Guajardo, of Calderon's National Action Party, or PAN, had received warnings to drop his campaign.
Several parties, including the PAN, had said they could not find anyone to run for mayor in some towns in Tamaulipas and other border states because of drug gang intimidation.
In the worst corruption scandal of the election, Cancun mayor Gregorio Sanchez was arrested last month for alleged drug trafficking ties, forcing him to drop his campaign for governor of Quintana Roo state. Sanchez was charged with protecting two of Mexico's most brutal drug gangs, allegations he has dismissed as politically motivated.
Calderon's government did not say which gang was suspected in Torre's assassination or why he would be targeted.
Tamaulipas, which borders Texas, has become a battleground between the Gulf cartel and its former ally, the Zetas gang of hit men. Gangs have staged bold attacks on security forces, ambushing army patrols and setting up blockades near army garrisons.
Tamaulipas state election authorities met to decide whether to suspend the vote.
The PAN and the leftist Democratic Revolution Part, or PRD, said they would suspend campaigning by their own gubernatorial candidates in Tamaulipas, but PAN party leader Cesar Nava said he hoped the vote would go forward.
PRI national leader Beatriz Paredes also indicated she wanted the elections to take place, urging supporters to go the polls. "Nothing is going to intimidate us," she said in a statement.
Torre, 46, was heading to the airport to fly to the border city of Matamoros, where he planned to attend the closing campaign events of the PRI's mayoral candidate, said Tamaulipas state Gov. Eugenio Hernandez. Four people were wounded in the attack, including Torres's personal secretary, Hernandez told Radio Formula.
Television footage from the scene showed several vehicles and sheet-covered bodies along the side of the highway.
Torre, 46, held a significant lead in polls as candidate for a coalition comprising two small parties and the PRI, which has long governed Tamaulipas.
George Grayson, a Mexico expert at the College of William & Mary in Virginia, said the assassination would almost certainly keep many voters home, but he expected the situation would only benefit the PRI.
"The execution and the ... climate of fear will dampen voter turnout on Sunday, which will help the PRI because they have the best political machine," he said.
The PRI, which ruled Mexico for 71 years before losing the presidency in 2000, is hoping that a strong showing in Sunday's elections will put it on the path to regain the presidency in 2012.
The conservative PAN has formed uncomfortable alliances with the PRD to oust the PRI from several states, though not in Tamaulipas. PAN and PRD politicians have insinuated that PRI politicians in Tamaulipas and other states have ties to drug gangs, allegations the PRI dismisses as tired campaign tactics.
Drug gang violence has rocketed since Calderon deployed thousands of troops and federal police across the country in 2006 to wage an all-out battle against cartels. Some 23,000 people have been killed in drug-related violence.
Torre, a physician, had served as the state's health secretary from 2005 to 2009. He was married and had three teenage children.
Associated Press Writers Olga R. Rodriguez and Mark Stevenson contributed to this report.