Mexico's top electoral court unanimously struck down a leftist coalition's bid to invalidate the July 1 presidential election, a ruling that clears the way for Enrique Peña Nieto to be sworn in as the country's next head of state.

The TEPJF electoral tribunal's seven justices presented separate arguments Thursday against the legal challenge brought by the Progressive Movement coalition against the victory by the candidate of the Institutional Revolutionary Party, or PRI.

They said insufficient evidence was submitted of biased and unequal coverage by the news media - particularly No. 1 broadcaster Televisa - in favor of Peña Nieto.

They also dismissed evidence of deliberate distortion in pre-election voter-preference surveys, use of illegal funding and excessive campaign spending, vote buying and coercion, improper intervention in the election by state governors and other public officials and irregularities on election day.

The election should not be invalidated because, after a review of the evidence, it was found that "constitutional principles were observed," Justice Salvador Nava said, adding that the July 1 election was free and authentic.

"Mexico has a legitimate president, elected by the people: Enrique Peña Nieto," Nava said.

In its general considerations, the court said it was not sufficient for the coalition - led by the Party of the Democratic Revolution, or PRD - to level generic accusations but rather it needed to spell out "clearly and precisely the circumstances of time, manner and place" in which the alleged abuses occurred.

PRI candidate Peña Nieto won the presidential election with 38.21 percent of the vote, while Progressive Movement candidate Andres Manuel Lopez Obrador took second place with 31.59 percent, according to the final official results released by the Federal Electoral Institute, or IFE.

But the Progressive Movement said that victory was tainted, alleging that the PRI used several front companies to purchase debit cards and then handed them out to millions of prospective voters to secure support for Peña Nieto.

Lopez Obrador's team said that through that chicanery the PRI exceeded campaign spending limits many times over.

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

National Action, however, did not formally contest the election results.

The non-partisan Yo soy 132 student movement also held a series of protests and other events to block the "imposition" of Peña Nieto as president.

After the TEPJF's ruling, hundreds of people protested Thursday night outside the courthouse in Mexico City, hurling security barriers and chanting slogans denouncing the PRI and Peña Nieto.

The demonstrators, who also held up signs reading "We Demand this Dirty Election Be Annulled" and "Peña Is Not President," did not spar with anti-riot police deployed nearby.

In statements to the media, Lopez Obrador's campaign manager, Ricardo Monreal, slammed the court's ruling.

He said the justices were a group of "frauds in robes and caps who are going to bury the constitution and go down as the most despicable group of puppets in the history of the nation's democracy."

Lopez Obrador, meanwhile, said early Friday that he did not accept the court's decision and called for "peaceful" civil disobedience.

He called for a demonstration on Sept. 9 in the Zocalo, Mexico City's massive main square, to define the left's next steps in the defense of "citizens' individual and social rights."

Following Thursday's ruling, the tribunal is now widely expected to confirm Peña Nieto as president-elect by September 6 at the latest.

Final confirmation of its victory will return the PRI to power after a 12-year absence.

The PRI, which governed Mexico from 1929 to 2000, lost the 2000 presidential election to the PAN 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.

Lopez Obrador also came in second in the previous presidential balloting in 2006, losing by the narrowest margin in Mexican history - a mere 0.56 percent of the 41 million ballots cast - to the PAN's Felipe Calderon.

He also said that contest was marred by fraud and declared himself to be Mexico's "legitimate president," organizing a series of marches over several weeks in Mexico City's Paseo de la Reforma, one of the capital's main thoroughfares. EFE