The apparent winner of Mexico's presidential race, Enrique Pena Nieto, struggled Monday with the sticky bonds of his party's notorious past, the limitation of his mandate and an opponent who has yet to concede defeat. 

His long-ruling and now-returned Institutional Revolutionary Party, the PRI, won only about 38 percent of the vote and is unlikely to get a majority in Congress. In fact, it may lose seats.

He faces an old guard in the PRI that still exercises considerable power, an ongoing war against fierce drug cartels and a still sluggish economy. His closest rival, leftist Andres Manuel Lopez Obrador, who polled a higher-than-expected vote of about 32 percent, has refused to accept the loss, and many of his militant followers are suspicious of the results.

President Barack Obama called Pena Nieto on Monday to congratulate him. The U.S. Embassy in Mexico City said Obama told him the United States "looks forward to advancing common goals, including promoting democracy, economic prosperity, and security in the region and around the globe, in the coming years."

Mexico's old rulers claim presidential triumph

Pena Nieto's account of the talk suggested his party has left behind the touchy nationalism of the past. He expressed interest in cooperation in security, commerce and infrastructure, but didn't bring up the traditional Mexican issue of U.S. immigration reform to help the 12 million Mexicans who live in the United States.

'Productive integration of North America'
Pena Nieto said he wanted "a relationship that will allow the productive integration of North America."

In Sunday's elections, Mexicans voted above all for a known quantity, the camera-friendly candidate of the party that ruled Mexico without interruption from 1929 to 2000.

But the PRI returns to power in unknown political terrain, where Mexico is more divided, more violent and less tightly controlled, raising the potential for political disputes on top of the drug war. The battle against drug cartels has already cost more than 47,500 lives and may have contributed to the decline of President Felipe Calderon's conservative National Action Party, whose candidate dropped to third place with about 25 percent of the preliminary vote count.

Pena Nieto pledged to continue that anti-drug offensive, but "with a new strategy to reduce violence and protect, above all, the lives of Mexicans." He promised there would be "no pact or truce" with drug cartels, but clearly some supporters expected the PRI to establish some sort of modus vivendi with the gangs, something party leaders were accused of doing in the past.

"He'll stabilize the cartels. He'll negotiate so they don't hurt innocents," Martha Trejo, 37, a PRI supporter from the Gulf coast city of Tampico, said at Sunday's victory rally.

Pena Nieto said Monday he will favor "well-aimed, precision strikes" against the cartels, and more cooperation with U.S. authorities, something that Calderon has already developed far beyond his predecessors.

Hope for new faces
The biggest immediate task facing Pena Nieto is to convince the 62 percent of voters who didn't vote for him that he is not planning a return to the corrupt, authoritarian and free-spending ways of the PRI of the past. Even some of Pena Nieto's supporters, such as school teacher Maria Santillan, 51, expressed hope he would surround himself "with new faces, people who aren't so corrupted."

All the potential conflicts were apparent at the victory rally just after midnight at the PRI's cavernous compound in Mexico City, where Pena Nieto was surrounded by graying holdovers from the PRI's glory days and a raucous crowd of supporters expecting jobs, hand-out programs and a quick reduction in drug violence.

"The PRI have learned to listen to the people, they have learned they are not kings ... to engage with people, understand them, and rule in a coalition with the people," said 20-year-old student Hector Perez.

"There is no return to the past," Pena Nieto said. "I am going to be a democratic president, who understands the changes the country has undergone in recent decades," he said in an apparent reference to reforms that created a more-level political playing field with energized civic organizations putting pressure on governments.

Pena Nieto promised a government "of national unity," but hasn't yet named any Cabinet choices, though he has said his campaign chief, Luis Videgaray, 43, would form part of his government team. Videgaray is well regarded by investors and seen as a possible choice for finance minister.

Nieto also suggested he would seek further internal reforms of his party, which for most of its history followed presidential dictates unquestioningly and rigged votes if it could not win elections that were already tilted sharply in its favor. The party liberalized in its final two decades, but it remained steadfast in protecting its leaders and stonewalling on probes of corruption.

Calderon was quick to recognize the PRI victory, and his party may serve as an ally in Congress in voting through some measures, such as Pena Nieto's call to open the state-owned oil sector to private investment. Pena Nieto told reporters Monday he would start working immediately on tax, energy and labor reforms, and would "sit down with the president (Calderon) ... to talk about what can be put forward before I take office" on Dec. 1.

But those very proposals, especially on the oil industry, have drawn the leftist Democratic Revolution Party, the PRD, into the streets for angry protests in the past.

Rival won't concede
PRD candidate Lopez Obrador has not conceded Sunday's elections, telling his supporters late Sunday, "You know these elections were not equitable," a reference to his allegations that Pena Nieto exceeded campaign spending limits and benefited from favorable coverage in Mexico's semi-monopolized television industry. Lopez Obrador has not said if he will challenge Sunday's vote results, but he led nearly two months of street blockades in Mexico City in 2006 to protest a narrow loss he attributed to fraud.

"We have information that indicates something different from what they're saying officially," Lopez Obrador said of the vote results, but added "We're not going to act in an irresponsible manner."

Lopez Obrador's party actually did better than pre-election polls had projected, winning apparent victories in three of the seven state elections on Sunday. The PRD was on track to win an overwhelming victory in Mexico City, the nation's capital and largest city, as well as taking the governorships of Morelos state to the south and the Gulf coast state of Tabasco, both of which were held by other parties. The PRI seemed to have taken the governorship of the western state of Jalisco from National Action.

Despite winning the presidency, the PRI may actually lose seats in Congress. The PRI-led coalition with the Green Party had about 38 percent of the congressional vote, with 95 percent of ballots counted on Monday. The coalition won about 46 percent in the last legislative vote three years ago.

Many Mexicans questioned why most pre-election polls underestimated support for Lopez Obrador by five or six percentage points, well outside those polls' margin of error. Lopez Obrador had claimed the polls were being manipulated, an accusation that accompanied frequent complaints that Pena Nieto was running a far more expensive campaign than his rivals.

Jorge Buendia of the polling firm Buendia and Laredo said some people who said they would vote for Pena Nieto appear to have changed their minds. There was also a surge in support for Lopez Obrador in the final days that couldn't be fully measured because electoral law effectively prohibits polling in the last week before the elections.

The PRI's victory appeared to be, above all, a triumph of pragmatism and power-broker politics. Few of those at his victory rally Sunday expressed the high-flown rhetoric about democratic transition and reform that were popular when National Action won the 2000 and 2006 elections. For its decades in power, the party excelled at handing out patronage jobs as well as work and business permits in exchange for votes.

Jaime Bernal, 48, who works as an aide to a PRI congressman, said at the rally the secret to the party's comeback was recognizing "the important thing for people is that they have something to eat, a job to support themselves."

But he also praised Pena Nieto's ease at working crowds, shaking hands and hugging people, a talent the party had lost during two decades of PRI presidents known as market-oriented "technocrats."

The Associated Press and Reuters contributed to this report.

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