Within sight of Mexico's fanciest shopping mall, surrounded by shiny new corporate office buildings and luxury-car dealerships, is a muddy and rutted 100-yard stretch of unfinished road that may have swallowed a presidential campaign.

An obscure legal battle over the road is threatening to scuttle the presidential aspirations of the country's most popular politician, Mexico City Mayor Andres Manuel Lopez Obrador.

Some analysts say Lopez Obrador is a victim of his own hubris for defying a court order to stop construction on the road, an access route to a new hospital. But others say his high-flying popularity and his populist rhetoric scare the nation's political establishment, who have pounced on a legal technicality to sabotage his run for president in 2006.

"I think he made the mistake of giving them an excuse, but they would have found something anyway," said Gabriel Guerra, a political analyst who said the nation's two dominant political parties -- President Vicente Fox's National Action Party, or PAN, and the Institutional Revolutionary Party, or PRI -- are desperate to knock Lopez Obrador out of the presidential running. "Their reading is that if they cannot prevent him from being on the ballot, he's going to win."

Lopez Obrador's legal and political woes have dominated the headlines and talk shows for weeks in a nation fixated on a presidential election nearly two years before the vote. As Mexicans have increasingly soured on Fox's conservative, pro-business administration, public opinion polls show that no other politician comes close to the popularity of the rumpled mayor, who portrays himself as a champion of the poor and is often likened to Brazil's populist leader, President Luiz Inacio Lula da Silva.

The mayor has said he believes that the nation's political and economic elite are out to get him. At a recent political rally, Lopez Obrador said they "get together to dine with fine wines to make decisions that hurt their fellow man." It is those elites "from above," Lopez Obrador has said repeatedly, who are behind what he has termed a "plot" to keep him out of the nation's highest office.

"The abuse of authority, the fraud and bad faith has been on the part of those who accuse me," Lopez Obrador said at the massive rally that filled the city's central square. "Everything has been fabricated to take away my political rights in 2006 and to stop the alternative national project that we are proposing."

Lopez Obrador has been stung by a series of disputes and scandals in recent months. He has been accused of ignoring the city's soaring crime rate and giving a family friend an exorbitantly-paid job as his chauffeur. The most damaging was a scandal earlier this year in which high-ranking members of his administration were caught on videotape accepting bribes from a wealthy businessman.

Then another administration official, who earns a modest salary, was videotaped as he gambled huge amounts of money in Las Vegas -- hardly the frugal image Lopez Obrador wants his government to project. No one ever admitted making the Las Vegas tapes, which Lopez Obrador said was more evidence of a conspiracy against him.

To drive the point home, the mayor this summer distributed 2.2 million copies of a comic book that claimed the "dark forces of evil" -- elites portrayed as snakes and sharks -- were out to get him, which led critics to say that Lopez Obrador was starting to sound paranoid.

Elected in 2000, Lopez Obrador's popularity soared because he pushed programs that were popular across class lines. He created social programs for the poor and cash handouts for the elderly, built new highways for middle-class commuters and enlisted wealthy business leaders, including Carlos Slim, Latin America's richest man, to invest millions in the restoration of the city's historic center.

But analysts said the scandals and Lopez Obrador's increasing class-based rhetoric have now cost him much support among the wealthy and the middle class. Claudio X. Gonzalez Laporte, head of a leading private sector association, told El Economista newspaper that it would be a "tragedy" if Lopez Obrador became president, saying that his economic policies were no more effective than "a letter to Santa Claus."

But well-to-do Mexicans are only a small sliver of the population. A national public opinion poll released last month by La Reforma newspaper found that 53 percent of those surveyed favored Lopez Obrador for president, followed by Interior Minister Santiago Creel of the PAN with 36 percent and Roberto Madrazo, president of the PRI, with 34 percent.

"If he can absorb the blows he's taken during the last six months and still be ahead in the polls, then he's going to remain a formidable candidate," said George W. Grayson, a Mexico specialist at the College of William & Mary in Virginia, who is writing a book about Lopez Obrador.

First he has to put the road issue behind him.

Just before Lopez Obrador took office on Dec. 5, 2002, the city expropriated property in the chic Santa Fe neighborhood for an access road to a new private hospital. The property's owners filed suit, claiming that the city had not followed proper legal procedures. After Lopez Obrador took office, a judge issued an order halting work while the matter was sorted out. Those who filed suit alleged that Lopez Obrador ignored the judge's order and continued construction, which the mayor denies. The disputed road is now completed, except for a short stretch.

The Mexican attorney general's office has asked Congress to strip Lopez Obrador's official immunity from prosecution, which would open the door for possible criminal charges against him for defying the judge's order. Mexican law bars anyone facing criminal charges from running for public office. Lopez Obrador has said that similar land disputes are rarely prosecuted, making the action against him a selective application of the law.

Some analysts said Fox, the PAN and the PRI are playing hardball politics that could backfire.

"This is all a pretext, and a blatant one," Guerra said of the road issue. "They're out to get him, of course, but they have taken it a step too far." He likened the situation to Venezuela, where a years-long effort by opponents of President Hugo Chavez ended in a resounding victory for Chavez in a recall referendum last month. Guerra said Chavez's opponents, like Lopez Obrador's, were largely members of the rich and powerful class who underestimated the power of his popular appeal.

Grayson said he doubted the PRI-dominated Congress would vote to strip the mayor's immunity. He said the PRI, which controlled Mexico for 71 years before Fox's election in 2000, would prefer to have at least three candidates in the 2006 race, requiring them to win with a little more than 30 percent of the vote to take power back. The PRI has been gaining ground in key state and municipal elections.

Grayson said PRI leaders believe there would be a popular backlash if Lopez Obrador appeared to be unfairly barred from running. "They hope to take him down a few notches," he said. "But an election in 2006 without Lopez Obrador would smell like month-old fish."

Mexico City Mayor Andres Manuel Lopez Obrador led a march of 150,000 supporters last month to protest efforts to strip his immunity from prosecution.This uncompleted road has emerged as a stumbling block to the presidential aspirations of Mexico City's mayor.