TOLUCA, Mexico — Mexico’s Institutional Revolutionary Party won the election for governor of the country’s most populous state in a landslide Sunday, strengthening the party’s bid to retake the presidency in national elections next year.

The populist party, which ruled Mexico for 71 uninterr

upted years before being voted out office in 2000, also scored apparent victories in gubernatorial elections in two other states: Coahuila and Nayarit.

But it was the election in the state of Mexico, which surrounds Mexico City, that had been most closely watched for signs of whether the PRI was gaining or losing momentum going into national elections.

Its current PRI governor, the telegenic Enrique Pena Nieto, is the early presidential front-runner and even though he wasn’t running in Sunday’s vote many will see the results as a barometer of his popularity.

And he must be pleased with the apparent win of his successor, Eruviel Avila, who had an almost 40 percentage point margin over his nearest rival.

With 68 percent of the ballot boxes counted, Avila had a 61.9 percent support, while Alejandro Encinas of the leftist Democratic Revolution Party, or PRD, had 21.5 percent and Luis Felipe Bravo Mena of President Felipe Calderon’s National Action Party had 12.7 percent.

Two private exit polls showed similar results.

One by Mendoza Blanco y Asociados, carried out for TV Azteca, had Avila with 64 percent support, Encinas with 23 percent and Bravo Mena with 13 percent. It also showed the PRI candidates winning in Coahuila and Nayarit. The poll had a margin for error of 4 percentage points.

A second poll by the firm Mitofsky, conducted for the Televisa network, had Avila with 60 percent support, Encinas with 28 percent and Bravo Mena with 12 percent. The poll did not provide of margin of error.

Avila thanked voters for the victory and said he would seek consensus as governor.

“Our party, the Institutional Revolutionary Party, understands clearly what these electoral results mean. The message they carry is responsibility,” said the party’s national leader, Humberto Moreira. “We are the party of the present and the future.”

Bravo Mena of the PAN conceded defeat, but Encinas refused to recognize the result and said he would legally protest the election. His party has filed complaints with the national elections tribunal over alleged PRI campaign violations.

In more than 80 years, the PRI has never lost the governorship of Mexico state, home to 15 million people and the sprawling, impoverished suburbs that ring Mexico’s capital.

Avila went into Sunday’s voting with polls giving him a 30-point advantage over Encinas.

While the PAN and the PRD had forged alliances for previous state elections in Oaxaca, Puebla and Sinaloa that helped them to defeat the PRI, they failed to strike such deals for Sunday’s trio of ballots.

The parties, instead, warned that a vote for the PRI would be a vote for a return to the past, when the “dinosaurs” wielded power through coercion, corruption and intimidation.

Across Mexico, many voters are weary of the PAN, which after more than a decade in power has failed to make fundamental changes in Mexico apart from a trademark war on organized crime that has seen a spike in violence. Since Calderon took office in late 2006, more than 35,000 people have died in drug violence, according to the government. Other sources put the number at more than 40,000.

And internal fighting in the PRD has left the leftist party in disarray.

The PRI has sprung back in the vacuum.

Euralia Contreras, 66, who voted at the same station as Avila, said that she was sure the PRI would win because it has tackled local problems and helped residents.

“I’ve received many benefits from (Avila),” Contreras said, referring to free canned foods the Avila campaign gave her. “The handouts came through. He has fulfilled his promises.”

Avila mounted one of the most expensive campaigns in Mexico’s history.

The newspaper Reforma reported last month that his campaign spent nearly 4.4 million pesos a day ($376,000), more than the 3.4 million pesos ($290,000) Calderon spent to win the presidency. The campaign didn’t respond to questions about spending from the AP.

For Fernando Pasillas Villarreal, there are no good candidates.

“I’ll vote, but only to cancel my vote, because I think that although the governor may change, the one who takes his place does not offer substantial improvements, and I still think that the PRI only enriches itself and enriches its friends.”

Election day had a bumpy start for some: Flooding caused by days of heavy rain forced officials to relocate more than 170 voting booths in two of the state’s largest cities, said Fabiola Bueno, a spokeswoman for the state’s electoral institute.

The relocation has affected more than 47,000 registered voters in Ecatepec and Nezahualcoyotl, just outside Mexico City, Bueno said. Tropical Storm Arlene dumped heavy rains on both cities Thursday, causing a river that carries sewage to overflow into residents’ homes.

Accompanied by his two children, Avila cast his vote in Ecatepec, the most populous city in the state where he served as mayor before becoming a gubernatorial candidate.

“I’m confident that today will be a fiesta for democracy,” he said.

Avila has not commented in recent days on the potential impact the Mexico state election could have on the PRI’s efforts to retake the presidency.

Asked Sunday whether the elections could give the PRI a boost ahead of 2012, Avila responded: “I’ll answer that when this election ends.”