MEXICO CITY -- About a quarter of a million people chanting "Fraud! Fraud!" jammed Mexico City's central square yesterday to back leftist presidential candidate Andres Manuel Lopez Obrador's bid to overturn his narrow electoral defeat with court appeals and mass marches.
Lopez Obrador told the rowdy but nonviolent crowd that he would present allegations of fraudulent vote tallies to the Federal Electoral Tribunal before today's deadline and demand a recount. He called for nationwide marches that would converge on Mexico City for another rally next Sunday as the seven-judge panel weighed his appeal.
"There is convincing evidence that they took votes away from us," Lopez Obrador said. "We are certain that we won on July 2, and we are going to defend our victory."
Many in the crowd said they were ready for a fight if Lopez Obrador did not prevail. "To the death!" shouted Maria Irene Ramirez, a 53-year-old retired railroad worker from Hidalgo state.
Yesterday's huge gathering, summoned on two days' notice, marks a critical point in what so far has been a peaceful challenge to the official result of the election, which gave governing-party candidate Felipe Calderon a winning margin of 244,000 votes out of 41 million cast.
Lopez Obrador, a fiery populist, has made a career of organizing mass demonstrations, and several of them turned violent in the 1990s. That legacy and the shrill tone of his statements last week have fed concern that the former Mexico City mayor could destabilize the country, undermining democratic institutions just six years after Mexico's emergence from decades of one-party rule.
But yesterday, he stopped short of calling for civil disobedience, eliciting groans from demonstrators when he asked them not to block highways.
"This is a peaceful movement, and we are never going to allow ourselves to be provoked by our adversaries," he said.
The crowd filled the vast downtown square, the Zocalo, and spilled into surrounding streets.
Mexico City police, subordinate to a government run by Lopez Obrador's Democratic Revolution Party, estimated the crowd at 280,000 people. Notimex, the semiofficial news agency of the conservative-led federal government, said slightly more than 200,000 people were present.
The challenger's party, known as the PRD, bused in party loyalists from around the country. Organizers said they came from 18 states as distant as Chiapas, on Mexico's southern border, and Southern Baja California.
They turned the Zocalo into a sea of yellow party flags and banners with slogans such as "No solution means revolution." They blew noisemakers, set off fireworks, and sang the national anthem.
Most political analysts say Lopez Obrador's campaign faces an uphill battle.
The European Union has said it found no evidence of major fraud or irregularity in the preliminary count last Sunday and the official count that ended Thursday.
Calderon, the candidate of President Vicente Fox's National Action Party, said Friday that he was not worried about a legal challenge to the election because irregularities found in the initial count were minor. He said he opposed a full recount.
Richard Boudreaux writes for the Los Angeles Times.