MEXICO CITY - Mexico's left-wing presidential candidate wants every single vote recounted and is threatening to call street protests as he fights an election result giving a razor-thin victory to his conservative rival.
Senior aides to Andres Manuel Lopez Obrador, a combative former mayor of Mexico City, said overnight they wanted a recount of Sunday's tight election to include every vote cast, not just the ballot returns reported by polling stations.
Lopez Obrador is first taking his challenge to election authorities but the aides said he could then bring out supporters to back his fight against results that just favor his ruling party rival, Felipe Calderon.
"We have full confidence that if the votes are counted, we will win the election," said Manuel Camacho Solis, the leftist's main political operator.
Mexico now faces two months of legal wrangling over the results, and the threat of street protests has raised fears of political unrest in a young democracy that is key to US interests over immigration, drug smuggling and security.
Left-wing militants remember a 1988 election when fraud was almost certainly robbed their candidate of victory and some are pushing Lopez Obrador to take his cause to the streets now.
"People don't want negotiation, they don't want us to accept the result but we have to guide the movement politically so it doesn't end up in a greater confrontation," Camacho Solis said.
Preliminary returns gave Calderon 36.38 per cent of the vote, 1 percentage point or about 400,000 votes ahead of Lopez Obrador, although the Federal Electoral Institute, or IFE, ordered a recount of polling station returns this week.
Lopez Obrador says 3 million votes were not accounted for and he refused to accept the preliminary numbers. Mexico's top election official, Luis Carlos Ugalde, said those missing votes were discounted because of errors made filling in ballots.
Lopez Obrador's Party of the Democratic Revolution, or PRD, has a team of experts pulling together evidence of irregularities in Sunday's vote.
The daily newspaper El Universal reported 10 ballot boxes and a polling station report were found in a garbage dump in a poor neighborhood on the edge of Mexico City.
Activists demonstrated outside offices of the government's prosecutor for electoral crimes on Tuesday, shouting against fraud and hanging a huge banner which said: "Ugalde: You deserve jail".
Mexico's election system has improved steadily over the last decade and is widely respected, but it now faces a serious test given the extremely tight presidential vote and the animosity between Lopez Obrador and Calderon.
Lopez Obrador campaigned on promises to put Mexico's poor first with new welfare benefits and infrastructure projects, and has made clear he will not give up without a fight.
"We are committed with the citizens to act, to defend the will of millions of Mexicans," he said on Monday night.
Calderon insists the preliminary returns are clear enough and his National Action Party, or PAN, will ask the IFE to declare him the winner on Wednesday.
He has promised pro-business reforms and would be a key ally of the United States in Latin America, where left-wing leaders critical of Washington have taken power in Argentina, Bolivia, Brazil, Uruguay and Venezuela in recent years.
Financial markets have jumped since the election with investors betting Calderon's apparent victory will hold.
Mexico's stock market jumped 4.8 per cent on Monday and gained 1.3 per cent on Tuesday. The peso currency has strengthened more than 2 per cent in the past two days.