SAO PAULO — Standing on the back of a small flatbed truck, Luiz Inácio Lula da Silva danced and waved and sang his way through a massive crowd of supporters that had gathered for a parade through the center of Brazil’s largest city on the day before the country’s presidential election.

Brazilians head to the polls Sunday in the first round of voting in a contest that has been marred by outbreaks of political violence and fears that far-right President Jair Bolsonaro, who has spent two years trying to undermine the election, will contest the results and refuse to leave power.

But da Silva, a leftist who served as president from 2003 to 2010 and holds substantial leads over Bolsonaro in pre-election polls, finished this stage of the campaign in a jubilant mood seemingly meant to persuade his supporters, his country and the world that the planet’s fourth-largest democracy would survive whatever final threat Bolsonaro may pose to it.

“I have no fear,” da Silva, 76, told reporters during a Saturday afternoon news conference. “If the people elect me, there will be an inauguration and everything else I’ve promised.”

Da Silva, a former trade unionist who became an icon of the Brazilian and global left during his presidency, has led Bolsonaro in nearly every poll conducted over the past year. His optimism received another boost on Saturday, when final pre-election surveys from Brazil’s two largest pollsters showed him leading Bolsonaro 51% to 37% and 50% to 36%, with other candidates lagging far behind.

That put da Silva in range of a resounding victory in Sunday’s first round: If he garners an outright majority of votes, he would end the election without the need for a runoff election against Bolsonaro on Oct. 23.

It would mark a triumphant return for Brazil’s first working-class president, who during his tenure oversaw an economic boom that lifted millions of Brazilians out of poverty and positioned Brazil as an emerging global superpower. He left office with approval ratings above 80%, and the title of “the most popular politician in the world” bestowed on him by U.S. President Barack Obama.

His legacy seemed forever tarnished by a corruption conviction that sent him to prison in 2017. Brazil’s economy, meanwhile, collapsed under da Silva’s chosen successor, President Dilma Rousseff, who was impeached in 2016.

But da Silva’s conviction was annulled in 2019, after The Intercept Brazil exposed judicial and prosecutorial malfeasance that bolstered da Silva’s argument that the investigation had been a politically motivated witch hunt against him and the leftist Workers’ Party all along.

That paved the way for a confrontation with Bolsonaro, a right-wing authoritarian who’d made vanquishing da Silva’s Workers’ Party and many of its favored policies, especially those that benefited poor and marginalized populations, his chief political aim.

For the last two years, Bolsonaro has sought to cast doubt on the election, seemingly convinced that his only path to victory over da Silva was to undermine faith in the contest and the election itself. He has spread conspiracy theories about voter fraud, waged an all-out battle with Brazil’s electoral institutions, and promised to “go to war” if he loses. He has said he will only accept the results if he believes the election is “clean and transparent.”

The threats from a former army captain with close links to the Brazilian military have generated widespread concern of a potential coup attempt, although most experts regard that as unlikely. Others have expressed fears of a Brazilian version of the Jan. 6, 2021, insurrection at the U.S. Capitol, an event Bolsonaro — a close ally of former U.S. President Donald Trump — and his allies have studied closely.

The combination of Bolsonaro’s conspiracies and his painting of the race as a battle of “good vs. evil” has contributed to a violent electoral atmosphere, during which multiple da Silva supporters have been attacked and killed by Bolsonaro backers. Da Silva has canceled events amid security concerns and ramped up his own protections. Polls, meanwhile, have shown that as many as a third of Brazilians are fearful of discussing their vote, a number that rises among supporters of da Silva’s Workers’ Party.

Voting is mandatory in Brazil, but there are concerns among some on da Silva’s side that fears of violence or political turbulence could keep some of his supporters away from the polls on Sunday. In recent weeks, da Silva has also sought to ensure turnout among Brazil’s poorest residents and to flip the votes of the roughly 15% of voters whom polls show still favor other candidates in the race.

His public parade Saturday, during which there was little visible security presence around him, seemed aimed at countering worries about violence and convincing his supporters to put an end to Bolsonaro’s presidency at the first available opportunity.

A first-round victory, many experts believe, could blunt any attempt from Bolsonaro to contest the results. Da Silva, meanwhile, argued that a definitive defeat of another far-right leader who has put democracy in his crosshairs would send a message to a global community that has largely rejected and isolated Bolsonaro thanks to the destruction of the Amazon rainforest and democratic erosion that has occurred on his watch.

“Brazil will enter into a moment of great peace, Brazil will return to a moment of great democracy, Brazil will return to a moment of extremely active and proud international relations,” da Silva said. “The message I can tell the world is that Brazil will wake up … with a more beautiful face. … Brazil has its heart and arms open to welcome the world again.”

Da Silva cast his ballot shortly before 9 a.m. in São Paulo, less than an hour after polls opened. Bolsonaro voted in his home state of Rio de Janeiro and will spend the day in Brasilia, the nation’s capital.

Polls will close at 4 p.m. Eastern time, with results expected within hours thanks to an all-electronic voting system that is widely considered one of the world’s most efficient and secure.

Top officials from the U.S. and European Union have expressed confidence in the Brazilian election system amid Bolsonaro’s threats, in an effort to help prevent a dispute. The U.S. Senate this week approved a resolution that called on the Biden administration to “review and reconsider its relationship with any government that comes to power in Brazil through undemocratic means.” EU lawmakers threatened trade sanctions against Brazil if Bolsonaro attempts to remain in power despite losing the election.

Despite da Silva’s optimism, Bolsonaro appears unlikely to simply accept defeat, whether it comes Sunday or in a runoff round three weeks from now. He and his supporters have questioned the legitimacy of the polls, and argued this weekend that Bolsonaro, not da Silva, is on the cusp of a first-round victory.

As many as a quarter of Bolsonaro’s voters do not want him to accept defeat, polls show, and many Brazilian observers consider it unlikely that he would do so after a campaign spent challenging the integrity of Brazil’s electronic voting system.

If the race does advance to a second round, it would “give Bolsonaro an extra month to cause as much turmoil as he can,” said Guilherme Casarões, a Brazilian political expert at the Getúlio Vargas Foundation in São Paulo.

Da Silva, however, pledged to celebrate the results of Sunday’s election even if he falls short of a first-round victory, especially as polls show that his lead over Bolsonaro would only expand in a head-to-head matchup.

“We’re going to party, because we deserve it,” he said Saturday. “To be reborn from the ashes is a reason to celebrate.”