MEXICO CITY — The landslide victory by Andres Manuel Lopez Obrador in Mexico's presidential election brought an abrupt end to the monopoly on power enjoyed by the Institutional Revolutionary Party, a nearly century-long dominance that cultivated corruption along with an extensive patronage system.

On Sunday night there were some tears, but no obvious shock or anger among the campaign workers streaming out of PRI headquarters after their candidate conceded the race within minutes of polling stations closing. Their party had finished a distant third.

Lopez Obrador, a populist and self-described leftist, had maintained a double-digit lead in the polls throughout the campaign, while PRI candidate Jose Antonio Meade's message had never gained traction.

So, what happened?

On the wide sidewalk in front of PRI headquarters, Ernesto Garcia Elizalde leaned on his cane considering that question and where the path forward might lie for the party he joined and has ardently supported since 1964.

Meade, a mild-mannered technocrat with Cabinet positions in multiple PRI administrations, had struggled in vain to address the issue of corruption, which Lopez Obrador made the central issue of a campaign that resonated strongly with Mexicans.

"There's no need to invent a hidden reason," said Garcia. "We know why we lost. We didn't lose because we had a bad fighter. We lost because of all the baggage we have."

As Meade campaign workers quietly slipped away after Sunday's loss, taunted by the celebratory honking of passing cars, Garcia lamented the PRI's half-dozen former governors who were either jailed or facing charges of corruption or organized crime ties.

"The people voted against the corruption that was generated and allowed to grow inside the party," he said.

With nearly 94 percent of the ballots counted, Meade had only 16.4 percent of the vote — a third of that won by Lopez Obrador. As recently as 1976, the PRI claimed 100 percent of the vote for its unopposed candidate.

The PRI was also on track to lose all the governorships at stake and even the bulk of the mayoral and congressional races in its last urban bastion, the state of Mexico, which nearly surrounds Mexico City.

A campaign staffer who requested anonymity to discuss the mood inside PRI headquarters said Sunday's result had been "anti-climactic" and compared it to the death of a very ill relative.

Everyone had known for some time what was going to happen, but when it finally did they were still not totally prepared, the staffer said. "That's what the whole campaign was like."

For decades, the PRI functioned as a serial dictatorship, with each all-powerful president serving six years and then choosing his successor, who would win in rigged elections.

When it lost the presidency for the first time in 2000 after a series of gradual democratic reforms, there was shock and visible anger among its members.

They dismissed the victory by the upstart conservative National Action Party and its candidates who had not come up through the ranks of the PRI, the traditional training ground for Mexican politicians, and scoffed at the idea that they could govern effectively.

And just as the PRI predicted, the two National Action presidents floundered, getting their initiatives through Congress only with the help of the PRI, which retook the presidency in 2012.

But the party blew its chance at a comeback with a string of corruption scandals that culminated in Lopez Obrador's victory on Sunday.

Party president Rene Juarez Cisneros seemed to be signaling the steps needed to repair the damage in a speech following Meade's concession. It was peppered with words like "responsibility" and "honesty."

"In the coming hours and subsequent days we must have a great call for deep reflection to find the path forward, to find the reasons and causes of these circumstances that we're facing today," he said.

Political scientist Jesus Silva Herzog said that while Sunday's loss was the most challenging yet for the PRI, it would be wrong to consider it a fatal blow.

"We have given the PRI up for dead many times," he said.

Nevertheless, after the 2000 loss, the PRI still had a very strong congressional presence. Now Lopez Obrador could cobble together a two-thirds majority in congress without even consulting the PRI.

"Today I have the impression that the PRI could be dispensable," Silva Herzog said.

Still, the party has rural strongholds. It could hang on for years in sparsely populated states where it still holds governorships, such as Campeche, Coahuila, Sonora and San Luis Potosi.

But even in those states, Lopez Obrador out-polled Meade, and the generous government funding the PRI uses to pay its staff and for advertising is likely to be seriously reduced since it is based on vote share.

People packing the streets Sunday night to celebrate Lopez Obrador's victory were not generous toward the PRI.

Waving a Lopez Obrador banner, 26-year-old law student Hugo Moreno declared: "The PRI is flailing like a drowning man."

Retired teacher Susana Zuniga advised the PRI to "sit down and learn from its errors."

Back at PRI headquarters, Garcia seemed to be doing just that, saying the party had to work harder to choose honest candidates who had not lost touch with its base.

"Its roots are very deep," Garcia said of the party. "It's going to take a lot of work not to reconstruct it, but to reunite it ... to reform a series of things, to get rid of the bad and leave the good."

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Associated Press writer Maria Verza contributed to this report.