The leader of Mexico's leftist Party of the Democratic Revolution, Andres Manuel Lopez Obrador, announced Tuesday that he has asked Mexico's Federal Election Institute for a recount of the ballots cast in Sunday's presidential election.
Lopez Obrador's demand came the day after he said the vote had been "plagued by irregularities."
Election authorities have projected Lopez Obrador as the runner-up in the vote.
Mexico's presumed president-elect, Enrique Peña Nieto, said Monday it was time for his country to leave behind the political rancor of campaign season.
The Federal Election Institute, known by its Spanish acronym IFE, says it expects the final count results Sunday. That's when each of the approximately 143,000 polling stations are supposed to have finished counting votes and signed an "act" detailing the number of votes.
Wednesday marks the beginning of the district count, in which each of the 300 electoral districts will scrutinize the acts.
Ballots will be recounted in cases where:
-- The difference between the first and second place candidate is 1% or less;
-- The number of annulled votes is greater than the difference between the first and second place candidates.
Ana Isabel Fuentes, international coordinator of information for IFE, said she expects the law to mandate recounts in 19 districts, representing about a third of the total ballots cast.
Lopez Obrador must wait until Sunday to formally submit any application for a recount to the Federal Election Tribunal. Any candidate can challenge, but National Action Party candidate Josefina Vazquez Mota has already conceded.
The PRD candidate's declarations echoed comments he made in 2006, when election authorities said the leftist candidate narrowly lost the presidential race to Felipe Calderon. Lopez Obrador claimed election fraud and never conceded, referring to himself afterward as "the legitimate president of Mexico."
At the time, his supporters protested nationwide. In Mexico City, they staged sit-ins and blockades.
In 2006, official results showed him losing by about 240,000 votes (or about 0.6%). He led marches and demonstrations and refused to concede; a partial recount was held.
Felipe Calderon was not declared president-elect until two months after the July election. Lopez Obrador did not accept that decision. A brawl broke out in the legislature before Calderon was scheduled to take the oath on December 1; Calderon sneaked in and out a back door to take the oath and gave the traditional speech not in Congress, but at another location.
On Monday, Lopez Obrador had called on his supporters to wait for the official results.
The Federal Election Institute's verification of individual poll results begins Wednesday.
But in an op-ed article published in Tuesday editions of The New York Times, Peña Nieto made it clear that he thinks the election is over and he has won. "Achieving our country's full potential is my mission as Mexico's next president," he wrote.
Earlier, Peña Nieto told CNN en Español he was ready to work across party lines to build a better Mexico.
"We have to be constructive and put aside our differences, which are only for competitions and electoral contests," Peña Nieto said Monday. "Yesterday I indicated that (after) this tense and divisive atmosphere, which is natural in all democratic contests, we have to turn the page and move on to enter another chapter, another moment in our political lives, with a willingness and spirit that are constructive and purposeful."
A quick count based on samples from polling stations throughout the country gave Peña Nieto the lead, with between 37.93% and 38.55% of votes, the Federal Election Institute said late Sunday.
On Monday, the presumed president-elect said he had been receiving congratulatory phone calls and messages from world leaders, including U.S. President Barack Obama.
Peña Nieto said he was unfazed by the fact that more than 50% of Mexicans had not voted for him.
"We, fortunately, live in democratic conditions with three predominant political forces, and this makes it very hard for any party to have an absolute majority," he told CNN en Español.
The projected victory for Peña Nieto marks a triumphant return to power for the Institutional Revolutionary Party (PRI), which lost its grip on Mexico's presidency to the conservative National Action Party in 2000.