Andres Manuel Lopez Obrador's followers set up dozens of makeshift camps that blocked most traffic on one of the main arteries in this megalopolis of 20 million people, snarling the already chaotic rush hour, slowing freeways to a crawl for miles and forcing millions of commuters to circle downtown looking for a way to work.
Insurance company employee Camilo Perez was among thousands who parked blocks away and hiked to work in business suits or high heels. He said his regular 40-minute commute took two hours.
"They should do this some other way," he said. "This is going to decrease the popularity of their fight."
Lopez Obrador called for the five-mile blockade at a demonstration of more than 500,000 supporters Sunday. He spent the night in a tent in the city's main Zocalo plaza. Thousands of his supporters hung protest banners from sculptures and pitched their own tents in the middle of Mexico City's historic, tree-lined Reforma boulevard.
Mexico City Mayor Alejandro Encinas, a member of Lopez Obrador's Democratic Revolution Party, said Monday his government wouldn't forcibly remove the protesters. President Vicente Fox's spokesman, Ruben Aguilar, said the federal authorities wouldn't step in, unless the city government requested their help.
Lopez Obrador offered his apologies Sunday "for any inconvenience our movement may cause."
Elio Mendoza, 49, a government employee, camped in a plastic tent without sleeping bags or blankets. Jubilant, he said sleep was the last thing on his mind.
"Sleep? The people have been asleep for too long," Mendoza said. "Today, we're happy, because the people have awoken."
Ruling party candidate Felipe Calderon emerged from the July 2 election with an advantage of less than 0.6 percent, or about 240,000 votes, over Lopez Obrador, a fiery leftist who promised to govern for the poor.
Lopez Obrador claims fraud robbed him of the victory. The Federal Electoral Tribunal has until Sept. 6 to declare a president-elect or annul the election.
There have been fears that the protests could turn violent as Lopez Obrador's supporters grow frustrated with the process that will determine the race's winner. Lopez Obrador has played on those fears, saying Sunday, "If democratic outlets are closed off, then all that's left is submission or violence."
Calderon, a conservative backed by big business, appeared before the electoral tribunal's seven judges on Sunday to argue that the election was clean and that a full recount was unnecessary and illegal.
"The question is whether we Mexicans are going to resolve our differences with pressure tactics and marches, or with reason and by the law," Calderon said in his statement to the court, which he released to the press.
He criticized the use of protests to try to sway the judges, saying, "We're in here to argue our case, not outside letting senselessness reign."
The protest's motley collection of tents and portable toilets contrasted sharply with the stock exchange, banks and other sleek, glass skyscrapers that line Reforma, where impromptu soccer and baseball games sprung up among the protesters.
"We hope that some day people will realize that we were right and we needed to do this," said 25-year-old dance student Tirso Vicente, one of thousands who spent the night.
Lopez Obrador's attorneys argued in a court hearing on Saturday that there were mathematical errors, falsifications or other problems at 72,000 of the country's 130,000 polling places.
The candidate accused Fox — who belongs to Calderon's National Action Party, and leaves office Dec. 1 — of fixing the race.
Lopez Obrador, who stepped down as Mexico City mayor last year to run for president, promised he would abide by the results of a recount, but again avoided saying what he would do if the tribunal refuses to order one.
The leftist candidate told the rally that "we won the presidency ... it is fundamental that they recognize my victory."
His supporters agreed, with one protester driving a truck carrying several live hogs eating out of feed buckets painted to look like ballot boxes. On the vehicle hung a sign saying, "This election was a pigsty."