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Enrique Peña Nieto was declared the legitimate winner of the Mexico's July 1 presidential election Friday by the country's highest electoral authority, formally opening the transition to a new government despite continuing claims of fraud by the second-place candidate of the left.

The Federal Electoral Tribunal said leftist candidate Andres Manuel López Obrador had failed to prove claims that vote-buying had affected the results of the vote returning Mexico's former autocratic ruling party to the country's highest office after a 12-year absence.

López Obrador told reporters Friday morning that he refused to recognize the results of the election and was calling for a peaceful protest that he described as "civil disobedience" on Sept. 9 in the Zocalo, the historic plaza in the heart of downtown Mexico City. He launched street demonstrations that paralyzed central Mexico City after he lost the 2006 vote, but widespread protests appear far less likely this time.

López Obrador said the electoral tribunal made an illegitimate ruling Thursday evening when it rejected the leftist's allegations of vote-buying and other campaign violations in favor of Peña Nieto, the candidate of the Institutional Revolutionary Party, or PRI. The seven electoral magistrates are nominated by Mexico's Supreme Court and confirmed by Congress and are widely seen as credible and non-partisan, although López Obrador has alleged that several members were based in favor of the PRI.

"I am telling the people of Mexico that I cannot accept the judgment of the electoral tribunal that declared the presidential election valid," López Obrador told a news conference. "The elections were not clean, free and genuine. As a result, I will not recognize an illegitimate power that's emerged as a result of vote-buying and other grave violations of the constitution and the law."

López Obrador, a popular former mayor of Mexico City, was able to call hundreds of thousands into the streets for campaign rallies, and he retains a large and fervent base of support in the capital. But Peña Nieto's margin of more than 3 million votes was far wider than the few hundred thousand votes that cost López Obrador the last presidential vote, and many opponents' outrage at Peña Nieto's win appears to have largely faded since the July 1 vote.

He said he wants the protest to respect the law, and he did not indicate that there would be a repeat of the blockades he launched in 2006.

By Friday afternoon, there were a few scattered protests around the capital by López Obrador sympathizers, including a brief blockage of highway toll booths by a group of students, but little evidence of widespread mobilization.

Confirmation of the PRI's victory returns the party to Mexico's highest office, which it held without interruption from 1929 to 2000. In past decades, the party engaged in widespread coercion of its opponents, monopolizing virtually every institution in the country. The party says it has reformed and handed control to a new generation of democratically minded young technocrats with a vision of modernizing Mexico.

Peña Nieto was expected to formally accept the status of president-elect within hours, officially beginning the country's transition to an administration that has promised to focus on fiscal reform, infrastructure improvements and a new emphasis on preventing violence from affecting ordinary Mexicans as a result of the country's six-year militarized offensive against drug cartels.

For much of his campaign, López Obrador tried to move away from the angry, combative image that many Mexicans held of him after his supporters blockaded much of downtown Mexico City for weeks after his narrow loss in 2006. He adopted the slogan "Abrazos, No Balazos," or "Hugs, Not Bullets," put forth a warmer persona, a more business-friendly platform and an anti-crime program that relies largely on increased jobs and education programs.

López Obrador did surprisingly well, gaining 31 percent of the vote to Peña Nieto's 38 percent after months of polls showed the PRI candidate with a lead as wide as 20 percentage points.

The unexpected closeness of the race helped fuel López Obrador's lengthy post-election fight to invalidate the results, with him and his backers accusing the PRI camp of a range of violations including the vote-buying with both gift cards and, in rural areas, farm animals, and participating in an international campaign finance money-laundering scheme.

The accusations centered on hundreds and possibly thousands of pre-paid gift cards that shoppers at a Mexican grocery store chain said they were given by Peña Nieto's party before the election. López Obrador's Democratic Revolution Party showed reporters thousands of such gift cards, but never publicly demonstrated convincing evidence that millions of votes had actually been swayed by corrupt practices.

The PRI said in a statement Friday morning that the ruling "has ended the contentious and combative phase of the federal electoral process and has fully demonstrated the legitimacy of Enrique Pena Nieto's victory at the ballot box."

Peña Nieto commented in his Twitter account that "now is the time to start a new stage of work, for the good of Mexico."

The electoral justices said some of the evidence submitted was hearsay, or unclear. For example, they said the evidence included gifts allegedly given out by the PRI, without proof that was where they came from or that the gifts had been given to influence votes.

"The evidence absolutely didn't support annulling an election with a difference of three million votes between first and second place," said José Antonio Crespo, an analyst at the Center for Economic Studies. "The left wants to be able to annul an election because of any irregularity. Rather, they want to where they lost, because in Mexico City and the legislature, where they did well, they don't want to, and it was the same election."

Ivan García Garate, a law professor at Iberoamerican University in Mexico City, said, however, that the electoral tribunal had adopted a very narrow view of its mandate and failed to conduct its own investigation of the charges, relying entirely on evidence presented by the left, and then declaring it insufficient.

Based on reporting by the Associated Press.

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