MEXICO CITY - Felipe Calderon's slim lead in Mexico's presidential race was called into question as an official recount of vote tallies showed his leftist opponent slightly ahead late Wednesday. However, Calderon insisted he had won and even offered to include his rival in his Cabinet.
With 90 percent of tally sheets recounted at 300 district headquarters across the country, former Mexico City Mayor Andres Manuel Lopez Obrador had 36 percent, compared with 35 percent for Calderon. The preliminary count completed earlier in the week had Calderon winning by 1 percentage point.
Officials from Calderon's ruling party said Lopez Obrador was only leading because more votes had been recounted in areas where he was strongest, and they insisted the trend would not hold.
They also accused the Lopez Obrador's party of stalling tactics in states where the conservative Calderon was strongest, saying it was deliberately trying to give the impression that Lopez Obrador was ahead as the count progressed.
Calderon campaign director Josefina Vazquez Mota told reporters Wednesday night that Lopez Obrador's slight lead would continue shrinking "until it is reversed and it is confirmed that Felipe Calderon has won the presidency."
Earlier on Wednesday, Calderon told the Associated Press in an exclusive interview he would be willing to include Lopez Obrador in his Cabinet - an effort to build a coalition government and avoid weeks of political impasse.
"Mexico needs us all," Calderon said. But he said he did not believe Lopez Obrador would accept, adding that the two men had not spoken to each other since Sunday's election.
Lopez Obrador insisted he was victorious and said there was "serious evidence of fraud."
Leonel Cota, president of Lopez Obrador's party, accused election officials of deliberately mishandling that count to confirm a win for Calderon, the ruling-party candidate. He said Lopez Obrador won Sunday's vote.
"We are not going to recognize an election that showed serious evidence of fraud, that was dirty from the start, manipulated from the start," he said.
When polls closed, citizens staffing the 130,488 polling places opened the ballot boxes and counted the votes, then sealed them into packages with their tallies attached and reported unofficial totals to the Federal Electoral Institute, or IFE. The institute then posted preliminary results on its Web site from about 41 million ballots cast.
The sealed packages were delivered to district headquarters, where elections workers used the tallies Wednesday to add up the formal, legal vote totals.
Workers were not reviewing individual ballots except when the packages appeared tampered with or their tallies were missing, illegible or inconsistent - including at least 2.6 million ballots likely to shrink Calderon's lead to 0.64 percent if included, election officials said Tuesday.
At one electoral office in Mexico City, officials opened a ballot box because the vote tally was missing. The votes were then re-counted out loud while 10 party representatives stood by with tape recorders and video cameras.
"I'm exhausted. I'm still tired from election day," said counter Rocio Sanchez, 41, an IFE employee. "But this is something we have to do by law."
Cota said Democratic Revolution would not recognize the results without a ballot-by-ballot recount. But IFE President Luis Carlos Ugalde said that was not possible.
"Mexican law is very clear on when a ballot box can be opened: only when there are problems with the vote tallies, when the tally sheet has obviously been changed, or when the box has been tampered with," Ugalde said.
Once the count is complete, the seven-judge Federal Electoral Tribunal hears any complaints and can overturn elections. By law, it must certify a winner by Sept. 6, and its decision is final.
Cota said the party might take its case to international tribunals.
Ugalde scolded both candidates for prematurely declaring victory, saying: "No political party can declare or affirm, at this time, that its candidate has received the largest number of votes."
Lopez Obrador called again Wednesday for his supporters to remain calm, but he could mobilize millions - as he has in past legal disputes - and he hinted Wednesday that he might.
"The political stability of the country hangs in the balance," he said.
In the AP interview, Calderon said demonstrations would be irresponsible.
"Elections are not won on the street," he said. "They are won in the voting places."
The review that began Wednesday is a crucial step in proving the elections were clean to a nation that emerged only six years ago from 71 years of one-party rule replete with election fraud. Failure to convince the public and candidates it has been a fair vote could spark widespread unrest.
"Such a close race is a nightmare scenario," said Ted Lewis, an election observer for the San Francisco-based Global Exchange. "If the ruling party wins by a hair, a lot of people will jump to the conclusion that something is amiss."
Most international observers said the election was fair and properly carried out by Mexico's world-renowned system, held up as a model to emerging democracies in Iraq and Haiti.
There have been fears that the battle over the presidency could turn violent. There were scattered protests Wednesday in favor of Lopez Obrador, all of them peaceful.
About 35 people set up camp Wednesday outside IFE's gates, draping banners that accused electoral officials of being traitors, and about 300 protesters marched down Mexico City's broad Reforma Avenue carrying a banner reading: "Respect Andres Manuel Lopez Obrador's victory!"
"We're not going to let them get away with this," said 62-year-old Enrique Flores, a retired Mexico City school teacher.
Associated Press reporters Ioan Grillo, Regina Reyes-Heroles and Will Weissert contributed to this report.