ÃO PAULO, Brazil Early in his political career, when his voice was gruff and his beard and hair were unkempt, Luiz Inácio da Silva sometimes campaigned in a T-shirt that warned, "I'm not in a good mood today."

But as he makes his fourth run to be president of Brazil, the eternal candidate of the leftist Workers' Party now favors elegantly tailored suits and tries hard to smile at audiences.

Whether Mr. da Silva's ideology has also changed is a more complicated matter. He has roiled markets here and abroad as he battles to maintain his current front-runner status until Oct. 6, when the first round of the election will be held.

In recent weeks, the Brazilian currency, the real, has hit one record low after another and the stock market has dived, driven by fears that Mr. da Silva and his party are still firebrand revolutionaries at heart and will govern that way if he becomes president of Latin America's largest country. A runoff is set for Oct. 27 if no candidate wins a majority on the first ballot.

Mr. da Silva, who is universally known here as Lula, says his socialist views have "evolved and mellowed." But foreign investors and the Brazilian middle class, whose votes he needs to win, continue to wonder whether his makeover is only cosmetic.

The candidate has responded by condemning the market speculation, which he calls "economic terrorism," even as he tries to reassure doubters.

"Look, if in the 22-year history of the Workers' Party I hadn't changed, something would be amiss," Mr. da Silva, a former labor leader, said recently. "I think that I've changed, changed a lot," he added, "and I think that the Workers' Party is also much more mature, much more conscientious."

Yet the causes of the skepticism that so exasperates Mr. da Silva are easy to discern. As the country's leading newsmagazine, Veja, pointed out in a recent article, nearly every reformulation of position Mr. da Silva has made in the current campaign "is followed by a qualifier clause" that seems intended to reassure the party's leftist base that he will not betray them.

"It is true that the Workers' Party is more moderate than it once was, but that doesn't calm people," Bolívar Lamounier, a leading political analyst, said in an interview here in the city that is the party's birthplace. "For 20 years, they have given the impression that they are more revolutionary than they really are, and now they are reaping what they sowed."

Mr. da Silva, who is 56, now promises that if elected he will do nothing to shake the confidence of investors. But his party is a fractious leftist agglomeration that ranges from an unrepentant Trotskyite faction nicknamed "the Shiites" to a group of European-style Socialists called "the pinks." Its platform demands a "necessary rupture" with Brazil's current economic model, to avoid "subordination to the interests and moods of globalized financial capital."

Mr. da Silva also says he will not default on Brazil's mounting foreign debt, a change from positions the party took as recently as last year. He does, however, promise to "renegotiate" those obligations as they fall due.

While Mr. da Silva says he is not against a free-trade zone in the Americas, he says Brazil will join only if he deems it "truly fair and just," and it does not exclude Communist Cuba.

Indeed, Mr. da Silva's popularity has surged along with the opposition to free markets that is rising across Latin America, as it becomes clear that the wave of privatization and deregulation of the 1990's did not bring prosperity, or even sustained growth.

"Each country has its own economic model, its own tax policy and development policy, and Brazil needs to build its own," he said. "Brazil can't be treated as if it were a colony. Brazil needs to think about what it wants, what the Brazilian people want."

In another effort to reach toward the center, in late June Mr. da Silva named a surprising running mate José Alencar, a textile magnate and senator who belongs to a small right-wing party affiliated with Protestant evangelical groups.

But the Workers' Party faithful attending the nominating convention booed and hissed the choice, and Mr. da Silva is now being accused of selling out by two presidential candidates further to his left.

Not wanting to stray off his message, Mr. da Silva has generally avoided situations in which he might be called upon to clarify contradictions in his platform. Over a 10-month period, he declined more than 20 interview requests from The New York Times. His chief media adviser, José Eduardo Mendonça, also declined to be interviewed.

But at a recent news conference with foreign reporters, Mr. da Silva dismissed the notion that three frustrating defeats since 1989 had encouraged him to try to sell a more palatable "Lula lite" in the current campaign.

"I've changed more in form than content," he said.

The president of the Workers' Party, José Dirceu, elaborated in an interview: "Our objectives continue to be the same, but the methods, the manner in which we reach that goal, have changed."

The main goal, Mr. Dirceu added, remained "a new social contract" that would end inequality and exploitation. Mr. da Silva "is not proposing socialism in Brazil," but the symbolism of the Workers' Party in power would be potent and inescapable, Mr. Dirceu noted.

Silva is perhaps the country's most common last name, and Mr. da Silva says he speaks in the name of the dispossessed masses, whose experience he has shared.

"First of all," Mr. Dirceu said, "to elect a president with the surname Silva, that is a very important cultural rupture in Brazil." Since Brazil became a republic more than a century ago, he said, "it has been only the elite that elects presidents and controls power in this country, and we need to break with that so there can be popular participation in the management of the state."

Mr. da Silva was born in the arid northeastern state of Pernambuco to a poor peasant family but, like millions of others from that region, he migrated to the industrial hub around São Paulo as a child. He became a factory worker at the age of 14, and lost part of a finger in an accident on the job. According to biographies, he was encouraged by an older brother who was both a Roman Catholic friar and a Communist Party member to become active in the labor movement.

It was his leadership of a series of metalworkers' strikes here during the late 1970's that projected him onto the national stage and made him the country's most prominent union leader. But with the exception of four years in the lower house of Congress, Mr. da Silva has never held elective office, leading opponents to question his ability to govern a complex, continental-size nation of 175 million people.

President Fernando Henrique Cardoso has seized upon Brazilian voters' jitters about the turmoil in surrounding countries to argue in favor of his handpicked candidate, former Minister of Health José Serra of the Brazilian Social Democratic Party, the party in power for the last eight years. Mr. Cardoso defeated Mr. da Silva in 1994 and 1998.

"If an incompetent president were to be elected, we could have the same fate as Argentina," Mr. Cardoso said last month.

But in a recent Brazilian press interview, the American ambassador to Brazil, Donna J. Hrinak, compared Mr. da Silva's rise from lathe operator to presidential hopeful as the Brazilian equivalent of the American dream.

"Lula has had to overcome a lot of things to get to where he is," she said.

Though Mr. da Silva has traveled extensively in recent years, some of his views of the world outside Brazil still seem based on stereotypes held by the Latin American left during the cold war. In a speech late last year in Cuba, he made it clear that he continued to support President Fidel Castro and his dictatorial government.

"Thank you, Fidel Castro, thank you for existing," he said. "Although your face is marked by wrinkles, Fidel, your soul remains clean because you have not betrayed the interests of your people."

Like his friend Hugo Chávez, the populist president of Venezuela, Mr. da Silva has been critical of the United States' efforts to defend itself from terrorism after Sept. 11.

"I think that to want to resolve the problems of humanity by making war is not the best experience for mankind," he said of the Bush administration.

Mr. Dirceu, his party's president, said that "no government headed by Lula is going to follow an anti-American policy, because that would be politically stupid." But he also made it clear that Mr. da Silva wanted Brazil to be more independent and assertive on the world stage.

"If the banks and the big corporations want a government in Brazil that is docile to financial capital and submissive to the State Department, then we can't help them," he said. "We'd rather lose the election than accept that."