DUQUE DE CAXIAS, Brazil — For many supporters of President Jair Bolsonaro, Sunday’s presidential election in Brazil can have just two possible outcomes: They celebrate or they take to the streets.
That is because, they say, his defeat can only mean the vote was rigged.
“There’s a lot of fraud,” said Kátia de Lima, 47, a store clerk at a rally for Mr. Bolsonaro this month. “It’s proven.”
At the same rally north of Rio de Janeiro, Paulo Roberto, 55, a government worker, said, “Anyone who votes for Bolsonaro is worried about the voting machines.”
And Fabrício Frieber, a lawyer from the state of Bahia, added, “Bolsonaro has been warning us.”
Throughout his presidency, Mr. Bolsonaro has methodically questioned and criticized the security of Brazil’s electronic voting system, despite the lack of credible evidence of a problem. Now, at the end of his first term, it is clear that his attacks have had an effect: Much of Brazil’s electorate has lost faith in the integrity of their nation’s elections.
Three out of four of Mr. Bolsonaro’s supporters trust Brazil’s voting system only a little or not at all, according to multiple polls over the past several months, including one last week. And in interviews with more than 40 of Mr. Bolsonaro’s supporters in recent months, nearly all said they were worried about election rigging and were prepared to protest if he loses.
Those doubts have undermined one of the world’s largest democracies and are likely to end up as one of Mr. Bolsonaro’s most pernicious legacies — part of a global trend of lies and conspiracy theories, often stoked by populist leaders and amplified by the internet, that are threatening democratic norms in the United States and across the world.
“Elections that you can’t audit? That’s not an election. It’s fraud,” Mr. Bolsonaro told reporters in July, citing a common claim about Brazil’s election system. “I’ll hand over power — in a clean election.”
If Mr. Bolsonaro is defeated and seeks to hold on to power, it appears that Brazil’s democratic institutions are prepared to resist. But it also appears that some of his supporters are prepared to fight.
“If our president isn’t elected, everyone goes to Brasília,” said Rogério Ramos, 40, owner of an automotive electronics shop, referring to the nation’s capital. “We shut down Congress, just like in ’64.”
In 1964, a military coup led to a violent, 21-year dictatorship in Brazil.
Many such warnings are likely off-the-cuff comments, rather than organized plans for violence. Law enforcement officials have not warned of any threat by groups in the event of Mr. Bolsonaro’s defeat.
But Brazil’s Supreme Court and electoral court have increased security, and the military is preparing for how to deal with potential unrest after the election, according to two senior military officials who spoke on the condition of anonymity to discuss private plans. The president or the courts could call on the military to try to control violent crowds.
Government officials, judges, journalists and much of the Brazilian public are worried about a scenario that resembles Jan. 6, 2021, when thousands of people stormed the U.S. Capitol in a bid to overturn the election results after former President Donald J. Trump repeatedly denied his loss.
Both Mr. Trump and Mr. Bolsonaro spent much of their administrations warning that the establishment was plotting against them. Mr. Trump railed against the “deep state,” while Mr. Bolsonaro has accused some of the judges who oversee Brazil’s Supreme Court and the country’s electoral court of trying to rig the election.
Mr. Bolsonaro has also questioned the security of Brazil’s electronic voting machines since 2015, after a center-right presidential candidate disputed a narrow loss. Then a congressman, Mr. Bolsonaro began a crusade that the voting machines were vulnerable to fraud because they are not backed up by paper ballots.
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Mr. Bolsonaro is right that Brazil’s voting system is unique. It is the only country in the world to use a fully digital system, with no paper backups.
Computer-security experts who study the system say that its design indeed makes it difficult to audit an election. But they also say that the system has numerous layers of security to prevent fraud or errors, including fingerprint readers, tests of hundreds of machines on Election Day, outside experts’ inspection of the source code and the fact that the machines do not connect to the internet, significantly reducing the chances of a hack.
Since Brazil began using electronic voting machines in 1996, there has been no evidence that they have been used for fraud. Instead, the machines helped eliminate the fraud that once afflicted Brazil’s elections in the age of paper ballots.
But those facts have not mattered much to Mr. Bolsonaro or many of the more than 50 million Brazilians who voted for him in the first election round. In interviews, Mr. Bolsonaro’s supporters instead focused their attention on a series of anecdotal apparent abnormalities in the voting process and results, as well as many conspiracy theories: machines steal votes from Mr. Bolsonaro; machines come preloaded with votes; some machines are planted fakes; officials manipulate vote tallies; and the vote results show suspicious patterns.
One man interviewed by The Times played a video he received on WhatsApp that said Mr. Bolsonaro had visited Russia this year to get President Vladimir V. Putin’s help in fighting the Brazilian left’s plans to steal Sunday’s election.
As in the United States and elsewhere, social media has helped polarize the population and enabled the widespread doubts about the elections.
Most of the Brazilian public used to gather around a single television channel, TV Globo. Now, Brazilians are splintered across the endless media landscape of the internet, often in bubbles with like-minded people that entrench pre-existing views, said Francisco Brito Cruz, director of the InternetLab, a research institute in São Paulo.
The public has even become part of the media themselves, creating and sharing memes and videos, including about the voting machines. In past elections, Mr. Bolsonaro’s supporters have gone to the polls searching for some irregularity to film and spread as further evidence of fraud.
“They’re on a wild good chase, trying to find where the poll worker is manipulating things, where they’re having problems,” Mr. Brito Cruz said. “They have convinced themselves, right?”
Most of Mr. Bolsonaro’s supporters said in interviews that they do not trust mainstream news outlets, which Mr. Bolsonaro has attacked as dishonest, and instead rely on news from a wide variety of sources on their phones, including social-media posts and messages they receive in groups on WhatsApp and Telegram.
“I look at the things I want to see, and I avoid looking at what they want to show me,” said José Luiz Chaves Fonseca, a turbine engineer for offshore oil platforms who was attending the rally this month north of Rio de Janeiro as a Bolsonaro impersonator. “If everyone thought like this, they wouldn’t be tricked.”
Many of the doubts about the election system are rooted in real events, but are twisted and framed as proof of something amiss. Mr. da Silva, for instance, was convicted of corruption charges, which were later nullified, so Mr. Bolsonaro and his supporters characterize him as a thief prepared to steal the vote.
Hackers infiltrated the computer network of Brazil’s election agency in 2018, and Mr. Bolsonaro and his supporters frequently cite the incident as proof of fraud. “If they say that the machines are so impenetrable, then why is someone in prison for breaking into a voting machine?” Alessandra Stoll Ranzni, a designer from São Paulo, said at the Brazilian version of CPAC, the conservative political conference, earlier this year.
An investigation showed the hackers were not able to gain access to voting machines or change vote totals.
Not all of Mr. Bolsonaro’s supporters are so skeptical. Vinícius Ramos, 32, a government worker north of Rio de Janeiro, said that he received a degree in a network security and felt differently than many of the people around him at a recent rally.
“The Brazilian national voting system is one of the safest in the world,” he said. “Just because I vote for him doesn’t mean that I agree with everything he says.”
André Spigariol contributed reporting from Brasília, and María Magdalena Arréllaga from Duque de Caxias, Brazil.