Mexico City ? The party of leftist presidential candidate Andres Manuel Lopez Obrador demanded a ballot-by-ballot recount Tuesday in Mexico’s closest-ever presidential race, claiming vote counts were manipulated and renewing fears of violent protests if the fiery politician does not get his way.

Lopez Obrador’s demand for a full recount of all 41 million votes cast in Sunday’s election set up a possible marathon showdown that could go to Mexico’s electoral courts, stirring memories of the bitter Florida recount in the 2000 U.S. presidential race.

“We are going to launch a battle for the legitimacy of the election,” said Leonel Cota, president of Lopez Obrador’s leftist Democratic Revolution Party, while the candidate trailed conservative Felipe Calderon by about 1 percentage point in preliminary tallies.

“We are convinced of the triumph of our candidate,” said Jesus Ortega, Lopez Obrador’s campaign manager. “We will demand a recount vote by vote, report by report, polling place by polling place.”

At the close of voting Sunday, volunteers at tens of thousands of polling places counted the ballots in each box and attached a report, sending it to district headquarters. A preliminary count of those tallies gave Calderon of the ruling National Action Party a 400,000-vote advantage over Lopez Obrador.

But electoral officials said Tuesday about 3 million ballots were not part of that count due to problems including ballots that were set aside for being incorrectly marked or appearing invalid. Lopez Obrador initially said such ballots were “missing,” but electoral officials said the ballots were in their control and would be examined – and counted if valid.

Officials said the uncounted votes included more than 743,000 for Calderon and nearly 889,000 for Lopez Obrador. If all 3 million votes were valid, it would reduce Calderon’s lead to 0.64 percent, they said.

Interior Secretary Carlos Abascal said recounting every ballot was “physically impossible and also legally impossible.”