Unlike his campaign events, it was conducted without the benefit of his party’s machinery, which used to truck in supporters from around the country, demonstrating a substantial base of hard-core support.  Saying that the economy will only get worse, Mr. López Obrador announced a campaign to press the government to cut wasteful spending, lower consumer prices and taxes, and do more for the poor.  “Our movement must continue demanding a change in economic policy, which has demonstrated its failure,” he said. “The model must be changed. You cannot put new wine in old bottles.”  The words clearly resonated with his poor and working-class base.  “We think he really can change things, so that people have the right to decide,” said Aide Florentino, 27, a member of a small garment cooperative in the rural southern part of Mexico City.  “It’s not important if López Obrador is the president,” said Víctor Baltasar, 49, who traveled to the rally from Guadalajara, where he is a supervisor for the city’s train system. “What’s important is that things change.”  But rising anxiety over the economy may be broadening his appeal. Despite government measures aimed at stimulating the economy and buffering households against the worst effects of the crisis, there is a widespread clamor to do more, from constituencies as varied as business groups and poor peasants and fishermen. That demand could alter the political calculus.  “Mexico is fundamentally a conservative country,” said Federico Estévez, a political analyst at the Autonomous Technological Institute of Mexico. “But in 2009, the cards are different.”  Referring to the left, he said, “I think they’re holding a wild card or a couple of aces.”  With the next presidential election three years off, Mr. López Obrador’s precise ambitions are unclear. He calls his new campaign a social movement and clearly aims to be a force to be reckoned with.  But his relationship with his own party remains fraught. Last year he lost a battle with a rival faction over the presidency of the party, the Party of the Democratic Revolution, or P.R.D., and he no longer holds any official position in the party or in government.  The low point came last fall, when most of the senators from his party broke with him to approve an important energy bill, as his supporters scuffled with police officers in an attempt to block the vote.  To many who had backed his presidential bid, Mr. López Obrador’s street-brawling political style had become a liability.  His campaign to overturn the results of the 2006 election, which he lost by only six-tenths of 1 percent of the total vote to Felipe Calderón, consisted of mass rallies and a tent city that shut major avenues in the capital for weeks. Refusing to concede, even after the country’s highest electoral court ruled in favor of Mr. Calderón, he held a grand public ceremony in which he had himself sworn in as the “legitimate president” of Mexico, a title he continues to claim.  Such antics have damaged the party’s reputation, officials say. Jesús Ortega, the party president, who defeated Mr. López Obrador’s choice for the post, said the party’s polling showed that two-thirds of Mexicans identified the P.R.D. as disruptive.  Moreover, the polls put the party in third place for midterm elections in July, when voters will elect all 500 members of Mexico’s lower house, the Chamber of Deputies. The party is currently projected to win 18 percent of the vote, half its showing in 2006.  While Mr. López Obrador’s popularity catapulted it in 2006 from the third largest to the second largest party in Congress, the party now stands to lose many of the seats it picked up then.  Mr. Ortega, while shying away from blaming Mr. López Obrador for the decline of the party, made it clear that he wanted to remake its image into that of a party closer to social democratic governing parties in Chile and Brazil, and that street blockades were not in the plans.  “Protests against injustice should not affect citizens’ rights,” Mr. Ortega said. “We have to learn to fight within the limits of the law.”  The party has begun running gauzy television spots asking voters for their forgiveness and declaring its willingness to work with other parties, a pointed contrast with Mr. López Obrador’s campaign of permanent harassment.  Publicly at least, Mr. López Obrador and his party say they have worked through their differences. Analysts say neither one can afford a split. “If the left as a whole doesn’t recoup before the elections on the basis of economic issues alone,” Mr. Estévez said, “then they really have no chance of ever ruling.”  Mr. López Obrador needs the structure and resources a large party provides, analysts said. And the party cannot jettison its most charismatic politician.  “The P.R.D. realizes they can’t give him up,” said Daniel M. Lund, a pollster who has done work for Mr. López Obrador, but not since 2004. “If the P.R.D. breaks with López Obrador, they will go to single digits.”  Where that leaves Mr. López Obrador’s movement is uncertain. Although 2012 is a long way off, none of the party’s current leaders have anywhere near his larger-than-life stature as a potential presidential contender.  What is evident is that while talk of a comeback may be premature, so was writing him off.  “He’s a charismatic, intuitive politician,” said Joy Langston, an analyst with the CIDE, a Mexico City research institution. “He not only knows how to win over the masses but also to govern in a way that continues his popularity. Amlo will never be completely finished.”  A version of this article appears in print on , on Page A10 of the New York edition with the headline: Economic Decline Lifts the Prospects Of a Vocal Populist. Order Reprints| Today's Paper|Subscribe
The dominant political figure of Mexico’s left seemed to be heading toward irrelevance, but the recession has created opportunities for his brand of economic populism.