MEXICO CITY — Mexico’s old guard prepared to sail back into power after a 12-year hiatus Sunday as the president of the long-ruling party said that all exit polls “irreversibly” favored its presidential candidate, Enrique Pena Nieto.

Three major exit polls showed Pena Nieto of the Institutional Revolutionary Party, or PRI, with about 40 percent of the vote in the presidential election, nearly 10 points ahead of his nearest challenger. Two were exit polls and the third a “quick count” based on the actual vote.

The Federal Elections Institute said that with 5 percent of the vote counted, Pena Nieto had 36 percent, Andres Manuel Lopez Obrador of the leftist Democratic Revolution Party had 31 percent and Josefina Vazquez Mota of the ruling National Action Party had just under 28 percent.

Vazquez Mota conceded, as did New Alliance candidate Gabriel Quadri, who had only single-digit support. That left Lopez Obrador as the single holdout as election officials prepared to release an official representative quick count at 11:45 p.m. local time.

PRI president Joaquin Coldwell said the party would await the official count before it declared victory.

At the PRI headquarters in Mexico City, a party atmosphere was building as sound technicians, waiters and an army of reporters waited in a large white tent in the party complex patio.  A norteno band broke out playing with Vazquez Mota’s concession. Pena Nieto, 45, had yet to arrive.

The party also appeared likely to retake at least a plurality in the two houses of Congress and some governorships.

Critics say the party’s 71-year rule was characterized by authoritarian and corrupt practices. But the PRI has sought to portray itself as a group that has been modernized and does not seek to a return to the old ways, and held a strong lead throughout the campaign.

“Enrique Pena Nieto appears to be accomplishing what many thought would never happen again: the return of a strong and dynamic PRI,” said Eric Olson of the Washington-based Mexico Institute. “The question: How will they govern?”

Lopez Obrador took hundreds of thousands of supporters to the streets in protest when he narrowly lost in 2006.

“We hope the candidate of the left will act with democratic maturity and also recognize the results,” Coldwell said.

Vazquez Mota garnered little more than 23 percent in exit polls released by Milenio and TV Azteca networks and quick count by Mitofsky. Lopez Obrador had about 30 percent of the vote.

The PRI has been bolstered by voter fatigue due to a sluggish economy and the sharp escalation of a drug war that has killed roughly 50,000 Mexicans over the past six years.

Hugo Rubio, 33, a municipal employee in Nezalhualcoyotl, says what he expects “more jobs, more tranquility in terms of security” under Pena Nieto.

“He has demonstrated that (the party) had changed, that he cares about the people who are most in need,” Rubio said at a red-clad crowd of supporters gathered with banner and balloons.

There were very few reports of problems during the vote, though some polling stations ran out of ballots and at least nine people were arrested in the southern state of Chiapas for trying to pass ballots pre-marked the PRI.

Interior Secretary Alejandro Poire said that across the country federal security forces were working closely with local and state authorities, as well as electoral officials, to guard the peace during the vote.

Sergio Ortega, 31, a Guadalajara businessman, said he would vote against Pena Nieto to try to prevent the return of the PRI.

“He had too much favoritism. They played many tricks,” Ortega said.

Pena Nieto has cast himself as a pragmatic economic moderate in the tradition of the last three PRI presidents. He has called for greater private investment in Mexico’s state-controlled oil industry, and has said he will try to reduce violence by attacking crimes that hurt ordinary citizens while deemphasizing the pursuit of drug kingpins.

Pena Nieto, who is married to a soap opera star, also has been dogged by allegations that he overspent his $330 million campaign funding limit and has received favorable coverage from Mexico’s television giant, Televisa.

University students launched a series of anti-Pena Nieto marches in the final weeks of the campaign, arguing that his party hasn’t changed since its days in power.

Pena Nieto says his party has abandoned the heavy-handed ways of the past and will govern in an open and pluralistic manner, and many say the PRI would not be able to re-impose its once near-total control even if it wanted to because of changes in society, the judiciary and Congress.

“The context has changed dramatically,” said Rodrigo Salazar, a professor at the Latin American Faculty of Social Sciences in Mexico City. “Society isn’t the same. It’s a very critical society, a very demanding society, with a strong division of powers.”