Mexico City —- Two years after an ultra-close election plunged Mexico into a summer of conflict, new evidence has emerged that casts further doubt on the results of the 2006 presidential election that declared Felipe Calderon the winner.

Jose Antonio Crespo, a columnist and political analyst with Mexico City's Center for Economic Research and Education, spent a year studying half of the 130,000 "actas" —- the official tally sheets from polling places.

In a new book, Crespo concludes that there were at least 316,539 and as many as 633,078 "irregular" votes, which included extra or missing votes reflected in the actas.

Calderon of the conservative National Action Party defeated leftist Andres Manuel Lopez Obrador by 233,831 votes, according to the final official tally declared in September 2006. Election officials declined to conduct a recount of all ballots, and Lopez Obrador charged massive fraud.

The episode recalled the emotional and legal furor in the United States following the disputed results of Florida balloting in the 2000 presidential election between George W. Bush and Al Gore.

"I'm not saying that Lopez Obrador won or that there was fraud," Crespo said. "But we can't know who won the election and the election should have been annulled ... What we want as citizens is certainty and [the electoral court] didn't give it."

Mexico's highest electoral court concluded that irregularities weren't severe enough to require annulling the election. The court ordered a recount of some 14 percent of the questioned votes.

Largely because of the lack of a full recount, millions of Lopez Obrador's supporters refused to recognize Calderon as the rightful winner. After the election, hundreds of thousands of Lopez Obrador supporters protested in the streets.

The public doubts have not faded with time. According to a recent poll, the number of Mexicans who don't believe the electoral conflict has been adequately resolved is growing.

A year ago, 39 percent of respondents thought the election conflict had yet to be resolved. Today the number has grown to 43 percent, according to the Consulta Mitofsky polling firm. Only 57 percent of Mexicans believe Calderon got the most votes.

Despite the lingering doubts over who really won the election, the Mexican government appears intent on burning, burying or shredding the questioned ballots, as is called for in Mexican election law.

Mexico's elections administrators, an agency known as IFE, and later the Mexican Supreme Court have rejected petitions by the Proceso political weekly magazine to conduct an unofficial recount, much as the American press did in the wake of the 2000 Florida presidential vote. That recount, which inspired the Mexican journalists, showed Democratic candidate Gore may have won Florida had there been a statewide recount.

Among the reasons given by Mexican elections officials and the courts in denying a recount was that it could affect national security and that ballots aren't "public documents."

Academics, including Crespo, have also filed petitions to open up the ballots for public viewing. The destruction of ballots is on hold until those cases are settled.

Meanwhile, Mexico's Congress passed a broad electoral reform in November 2007. But Crespo says the new law, which calls for recounts by electoral districts, wouldn't have removed the doubt if it were applied to the 2006 election.

"If this happens again in the future, the new law won't resolve anything," Crespo said.

WHERE THEY ARE NOW

President Felipe Calderon

So far, most analysts say he has done well in office, given the disputed election results and the emotionally charged environment in which he took office. His approval rating stands at 61 percent, and he has the magic touch when it comes to shepherding pension and tax reforms.

His most serious test is energy reform, an issue that has re-energized his opposition.

While he gets points for confronting Mexico's drug cartels, economic worries have leapt to the forefront. In June, the lackluster economy was the public's top worry, outpolling crime concerns.

Mexico has a single-term limit for president, so Calderon cannot seek reelection. A potential successor for the 2012 race from his National Action Party has yet to emerge.

Andres Manuel Lopez Obrador

After the election drama, Lopez Obrador created a symbolic "parallel" government, installing himself as the "legitimate president" and touring Mexico incessantly to build support.

He has seized upon the ongoing debate over reforming Pemex, Mexico's nationalized oil concern, to return to the public eye. He has promised mass mobilizations if legislators pass energy reform, which he has called "privatization."

His Democratic Revolutionary Party is expected to finish a distant third in next year's congressional elections. Some want a more pragmatic party willing to negotiate with Calderon's government.

Lopez Obrador is still the frontrunner for his party's nomination for the 2012 presidential race, but his protege, Mexico City Mayor Marcelo Ebrard, is seen as a serious threat.