He’s Back From Prison. Now He Could Be Brazil’s President — Again.

RIO DE JANEIRO — In 2019, Luiz Inácio Lula da Silva was spending 23 hours a day in an isolated cell with a treadmill in a federal penitentiary.

The former president of Brazil was sentenced to 22 years on corruption charges, a conviction that appeared to end the storied career of the man who had once been the lion of the Latin American left.

Now, freed from prison, Mr. da Silva is on the brink of becoming Brazil’s president once again, an incredible political resurrection that at one time seemed unthinkable.

On Sunday, Brazilians will vote for their next leader, with most choosing between President Jair Bolsonaro, 67, the right-wing nationalist incumbent, and Mr. da Silva, 76, a zealous leftist known simply as “Lula,” whose corruption convictions were annulled last year after Brazil’s Supreme Court ruled that the judge in his cases was biased.

For more than a year, polls have shown Mr. da Silva with a commanding lead. Now a surge in his numbers suggest he could win outright on Sunday with more than 50 percent of the vote, avoiding a runoff with Mr. Bolsonaro.

A victory would complete a remarkable journey for Mr. da Silva, whom former President Barack Obama once called “the most popular politician on Earth.” When he left office in 2011 after two terms, Mr. da Silva’s approval rating topped 80 percent. But then he became the centerpiece of a sprawling investigation into government bribes that led to nearly 300 arrests, landing him in prison and seemingly destined for obscurity.

Today, the former union leader is back in the spotlight, this time poised to retake the wheel of Latin America’s largest nation, at 217 million people, with a mandate to undo Mr. Bolsonaro’s legacy.

“How did they try to destroy Lula? I spent 580 days in jail because they didn’t want me to run,” Mr. da Silva told a crowd of supporters last week, his famously gravelly voice even hoarser with age and a grueling campaign. “And I stayed calm there, preparing myself like Mandela prepared for 27 years.”

On the campaign trail, Mr. da Silva has taken to comparing himself to Nelson Mandela, Mahatma Gandhi and Martin Luther King Jr., political prisoners who expanded their movements after they were freed. “I am convinced the same thing will happen here in Brazil,” he said at a separate rally this month.

Mr. da Silva’s return to the president’s office would cement his status as the most influential figure in Brazil’s modern democracy. A former metalworker with a fifth-grade education and the son of illiterate farm workers, he has been a political force for decades, leading a transformational shift in Brazilian politics away from conservative principles and toward leftist ideals and working-class interests.

The leftist Workers’ Party he co-founded in 1980 has won four of the eight presidential elections since the end of Brazil’s military dictatorship in 1988, while finishing as the runner-up in the rest.

As president from 2003 through 2010, Mr. da Silva’s administration helped lift 20 million Brazilians out of poverty, revitalized the nation’s oil industry and elevated Brazil on the world stage, including by hosting the World Cup and Summer Olympics.

But it also allowed a vast kickback scheme to fester throughout the government, with many of his Workers’ Party allies convicted of accepting bribes. While the courts threw out Mr. da Silva’s two convictions of accepting a condo and renovations from construction companies bidding on government contracts, they did not affirm his innocence.

Mr. da Silva has long maintained that the charges were false.

If Mr. da Silva wins the presidency, it will be in part thanks to an old-school campaign. He has toured the vast country holding in-person rallies. He has played it safe, skipping a debate last Saturday, offering few specifics in his proposals and declining most interview requests, including with The New York Times.

And he has built a broad coalition, from communists to businessmen, selecting a former center-right governor as his running mate, Geraldo Alckmin, who had been his opponent in the 2006 presidential election.

Mr. da Silva has also benefited from a matchup with a deeply unpopular incumbent. Polls show that about half of Brazilians say they would never support Mr. Bolsonaro, who has upset many voters with a torrent of false statements, destructive environmental policies, an embrace of unproven drugs over Covid-19 vaccines and harsh attacks against political rivals, journalists, judges and health professionals.

On the campaign trail, Mr. Bolsonaro has called Mr. da Silva a crook and a communist, while Mr. da Silva describes the president as authoritarian and inhumane.

If elected, Mr. da Silva would be the most significant example yet of Latin America’s recent shift to the left. Since 2018, leftists have ridden an anti-incumbent wave into office in Mexico, Colombia, Argentina, Chile and Peru.

Overall, Mr. da Silva’s campaign has been built around the promise he has been pitching for decades: He will make life better for Brazil’s poor. The pandemic battered Brazil’s economy, with inflation reaching double digits and the number of people facing hunger doubling to 33 million. He has pledged to widen the safety net, increase the minimum wage, lower inflation, feed and house more people and create jobs through big new infrastructure projects.

“He was the anti-poverty president, and that’s the legacy he wants to keep if he wins,” said Celso Rocha de Barros, a sociologist who wrote a book about the Workers’ Party.

Yet, like most successful politicians, Mr. da Silva’s speeches are often short on details and long on promises. He frequently builds his rhetoric around a clash between “they,” the elites, and “we,” the people. He wears his working-class credentials on his left hand; he lost his pinkie at 19 in an auto-parts factory. And he carries his message with his Everyman image, complete with plenty of references to beer, cachaça and picanha, Brazil’s most famous cut of meat.

“They think that the poor don’t have rights,” he told a crowd of supporters in one of São Paulo’s poorest neighborhoods last week. But he would fight for their rights, he said. “The right to barbecue with family on the weekend, to buy a little picanha, to that piece of picanha with the fat dipped in flour, and to a glass of cold beer,” he shouted to cheers.

“He’s the candidate of the people, of the poor,” said Vivian Casentino, 44, a cook draped in the red of the Workers’ Party, at a rally this week in Rio de Janeiro. “He’s like us. He’s a fighter.”

In his first stint as president, Mr. da Silva used a commodities boom to pay for his expansion of government. This time around, Brazil’s economy is in rougher shape, and he is proposing higher taxes on the rich to fund more benefits for the poor. Some voters are uneasy with his plans after his handpicked successor’s economic policies helped lead Brazil into a recession.

While his political style has not changed in his sixth presidential campaign, he has tried to modernize his image. He has included more references to women, Black people, Indigenous groups and the environment in his speeches and proposals, and even promised to advocate for “organic salads.”

At a recent meeting with social-media influencers, including the nation’s most popular YouTuber, a sharp-witted comedian and a rapper with face tattoos, Mr. da Silva urged them to counter suggestions that he was corrupt.

“Globo spent five years calling me a thief,” he said, referring to Brazil’s biggest TV network. He said he wished the channel’s lead anchor would open the newscast one night by saying sorry. “Apologies are hard,” he added.

Mr. da Silva has never fully acknowledged the role of his Workers’ Party in the government corruption scheme that persisted for much of the 13 years it was in power. The investigation, called Operation Carwash, revealed how companies paid hundreds of millions of dollars in bribes to government officials in exchange for public contracts.

Mr. da Silva says that political enemies framed him to eliminate the Workers’ Party from Brazilian politics. He has also accused the U.S. government of helping to drive the investigation.

The Carwash investigation was eventually engulfed in its own scandal, as it became clear that it had been used as a political tool. Prosecutors focused on the crimes of the Workers’ Party over other parties, and investigators leaked Mr. da Silva’s taped conversations. Sergio Moro, the federal judge overseeing the case, was later revealed to be colluding with prosecutors, while also acting as the sole arbiter in many of the trials.

In 2019, Mr. da Silva was released from prison after the Supreme Court ruled he could be free while pursuing appeals. Then, last year, the Supreme Court threw out his convictions, ruling that they were tried in the wrong court and that Mr. Moro was biased.

Mr. da Silva is carried by a cult of personality, built over more than four decades in the public eye, and he is far more popular than the political party he built.

Creomar de Souza, a Brazilian political analyst, said immature democracies can often revolve around a single personality rather than a movement or set of ideas. “Some young democracies struggle to take a step forward,” he said. “An individual becomes a crucial part of the game.”

At a rally for Mr. da Silva in Rio this week, Vinicius Rodrigues, 28, a history student, was handing out fliers for a communist party. “We support Lula specifically,” he said, but not the Workers’ Party.

Nearby, Luiz Claudio Costa, 55, was selling “I’m with Lula” headbands for 50 cents. He had always voted for Mr. da Silva, but in 2018, he chose Mr. Bolsonaro. “I got it wrong,” he said. “We need Lula back.”