The move by Andres Manuel Lopez Obrador, who appears to have narrowly lost the vote to ruling party candidate Felipe Calderon, comes a day after the fiery leftist held a massive rally in Mexico City's historic center and called on his supporters to help keep his hopes alive.

The evidence to be presented to the Federal Election Tribunal includes alleged proof of computer manipulation of results and that votes weren't counted, his party says.

The legal appeals won't seek to annul the July 2 election, but to force authorities to conduct a manual vote-by-vote recount. Over 100,000 supporters rallying in Mexico City on Saturday chanted "vote by vote!"

Election officials say Calderon beat Lopez Obrador by less than 244,000 votes out of 41 million ballots - or a margin of about 0.6 percent.

But Lopez Obrador remains convinced he won. He has millions of devoted followers who believe only he can help Mexico's poor and downtrodden, and he views street protests as an effective means of pressuring the government and the courts.

Lopez Obrador's claims include allegations that President Vicente Fox used government funds to support Felipe Calderon, the candidate of Fox's conservative National Action Party.

Fox has denied intervening in the elections, and election monitors from the European Union said they found no irregularities in the count.

But the allegations strike a sensitive nerve with many Mexicans who still question whether the nation has overcome the decades of institutional corruption and fraud that favored the ruling party. Lopez Obrador has stoked those fears.

On Saturday, he accused the respected Federal Electoral Institute, held up as an example to emerging democracies around the world, of being a "pawn of the party of the right."

Fox "dedicated himself to attacking us and ended up being a complete traitor of democracy," Lopez Obrador said.

Representatives for Fox and Calderon were not immediately available to comment. Fox has stayed out of the public eye in the past two weeks, an effort to avoid accusations that he is meddling in the debate.

The leftist former Mexico City mayor also said a previously arranged software program was used to skew initial vote-count reports - similar to the alleged computer crash that flipped Mexico's 1988 elections in favor of the ruling party at the time.

Legal challenges were built into Mexico's elections process in recent years to help ensure clean elections, so Calderon can't be declared president-elect until the electoral court weighs allegations of fraud or unfair campaign practices. The court has until Sept. 6 to declare a winner.

Lopez Obrador claims include allegations that votes weren't counted or voided without reason.

The law allows a manual recount only for specific polling places where credible evidence of irregularities exist. The leftist's supporters say that applies to at least 50,000 of the approximately 130,000 polling places.

Calderon says the vote was clean and has taken congratulatory phone calls from U.S. President George W. Bush and the leaders of Canada, Spain and Colombia, among others - despite Lopez Obrador's plea for foreign governments to hold off on recognizing the result.

"We are going to ask that they clean up the elections. We are going to ask that they count all the votes, vote-by-vote, poll-by-poll," Lopez Obrador said. He claimed the election fraud was worse than under the Institutional Revolutionary Party, or PRI, which ruled Mexico from 1929 to 2000, often using fraud to hold power.

Lopez Obrador provoked groans of disappointment from the crowd packed into the capital's central plaza on Saturday when he told them not to block highways.

"This has been and goes on being a peaceful movement," he said. "We are not going to fall for any provocations."

But Lopez Obrador has repeatedly evaded questions about whether he would accept court decisions that go against him, and said "a victory for the right is morally impossible."

Also Sunday, the Federal Electoral Institute will certify the results of the July 2 election and wrap up vote tallies that will determine the number of seats each party has in Congress.

According to calculations by Mexican media based on a preliminary vote count, Calderon's National Action Party will be awarded 210 seats in the lower house, while Lopez Obrador's leftist alliance with have 163 seats and an alliance led by the PRI will have 113 seats. Another 14 seats will go to minor parties, according to these calculations, which have not been certified by electoral officials.