The Institutional Revolutionary Party, or PRI, slammed the Mexican left's insistence that the July 1 presidential election be overturned and an interim president be named to organize a new vote as "absolutely out of line."

Andres Manuel Lopez Obrador, who was the candidate of a leftist coalition led by his Party of the Democratic Revolution, or PRD, said in a press conference earlier this week that the election must be invalidated due to massive vote-buying by the PRI.

But Pedro Joaquin Coldwell, chairman of the PRI - whose candidate, Enrique Peña Nieto, won the contest with 38.21 percent of the vote, according to the final official tally - said Friday that Lopez Obrador is out to discredit a "democratic and transparent" election.

"It's a repeat of Andres Manuel's same nonsense of six years ago," Joaquin Coldwell said, referring to Lopez Obrador's refusal to accept his narrow defeat in the 2006 presidential contest to Felipe Calderon of the National Action Party, or PAN.

Lopez Obrador said that year's balloting also had been marred by fraud, declared himself to be Mexico's "legitimate president" and organized a series of marches over several weeks in Mexico City's Paseo de la Reforma, one of the capital's main thoroughfares.

"So let's start preparing now because when he loses the 2018 election, he'll once again call for an interim presidency," the PRI chairman said.

The PRI also has made tit-for-tat allegations against Lopez Obrador in recent days, accusing his Progressive Movement coalition of using grassroots organizations as "parallel structures" to evade campaign finance rules.

Lopez Obrador, who took second place in the vote with 31.59 percent, has mocked those claims, saying "scoundrels think everyone's a scoundrel."

In his press conference Thursday, the leftist said that "if the election is not invalidated, Mexico will be governed by a band of criminals, the most corrupt and terrible in the country."

He proposed that the lower house of Congress choose an interim "honorable president to convene new elections within a period of 15 to 18 months, at the latest," rejecting the notion that such a process would lead to "instability."

"I assure you that it will be worse for us as a nation if there is impunity, if it's decided there will be a president ... who comes to office by buying the presidency of the republic," Lopez Obrador said.

The leftist hopeful filed a motion last week with Mexico's TEPJF electoral court seeking to have the election overturned, contending that the PRI effectively bought 5 million votes, or more than the margin of victory of roughly 3.3 million ballots.

The TEPJF has until the end of August to either officially certify Peña Nieto as president-elect or annul the election.

Lopez Obrador is basing his motion to invalidate the vote on an article of the constitution stating that elections must be "clean and authentic," an argument that legal experts say the TEPJF is unlikely to accept.

The leftist also said this week that Calderon's administration may be concealing evidence of wrongdoing by the Peña Nieto campaign.

"They're not going to be able to cover up the pigsty, so it's better that we come to an agreement to see how we're going to resolve this matter," he added.

The PAN, whose candidate, Josefina Vazquez Mota, finished a distant third in the presidential election, also has joined with Lopez Obrador in demanding an investigation of the PRI's finances.

The ruling party approached electoral authorities on June 14 with a request to freeze the PRI's accounts with Monex bank on suspicion that PRI operatives handed out prepaid debit cards issued by that financial institution in an apparent attempt to buy votes.

The PRI has acknowledged using debit cards to pay party workers, but says it did not enter into any contract with Monex.

The PAN, however, has said it is not contesting the election results.

The non-partisan Yo soy 132 student movement, for its part, has joined Lopez Obrador in challenging the outcome of the July ballot and has announced a series of protests and other events to block the "imposition" of Peña Nieto as president.

Thousands of Yo soy 132 members and supporters surrounded the Mexico City headquarters of Televisa, the country's dominant television broadcaster, for 24 hours starting Thursday night, chanting slogans against Peña Nieto and the PRI and holding up signs saying: "Televisa lie factory" and "We want schools, not soap operas."

Yo soy 132 emerged in May, largely as a reaction to the Mexican mass media's bias in favor of Peña Nieto and the PRI.

The PRI, which governed Mexico from 1929 to 2000, lost the 2000 presidential election to National Action and finished third in 2006.

During its 71-year reign - described by Peruvian Nobel literature laureate Mario Vargas Llosa as the "perfect dictatorship" - the PRI relied mainly on patronage and control of organized labor and the mass media, though it was not above resorting to outright vote-rigging and even violence. EFE