Leaders in Brazil’s Congress, courts and armed forces have said that they would not abide by any efforts to reject voters’ will, but many say privately that they are concerned that Mr. Bolsonaro’s supporters will react violently to a loss. In July, three out of every four supporters of Mr. Bolsonaro told Brazil’s most prominent polling company that they trusted the voting machines only a “little” or not at all.
There is no evidence of past widespread fraud in the system.
On Wednesday night, news of the document quickly spread among Mr. Bolsonaro’s supporters on social media, with people sharing right-wing articles about the allegations and conspiracy theories that said it proved what Mr. Bolsonaro had been alleging. One YouTube video about it quickly attracted more than 100,000 views in just a few hours. A conservative congresswoman, Carla Zambelli, was one of the first to post the document on social media, sharing it with her 1.9 million followers on Twitter.
However, many other politicians, including Mr. Bolsonaro, did not mention it online. In its statement on Wednesday night, the electoral authority reminded elected officials and candidates that they could be impeached or prohibited from running if they shared false allegations about the voting system. That swift reaction likely prevented wider dissemination of the document among politicians.
Election officials could also revoke the registration of Mr. Bolsonaro’s conservative political party, called the Liberal Party, if it was found guilty of spreading misinformation about the voting systems, though that would only happen after the election.
The document said that the July audit found 24 flaws in the election system’s security. A rough summary of the audit, it specified just a few of those alleged flaws, including that election officials used poor cybersecurity policies, that they did not properly vet relationships with suppliers and that they did not fully protect the employees who control the machines’ computer code from “irresistible coercion.”
Election officials’ delay in fixing those alleged security gaps “could result in internal or external breaches of the electoral systems, with a serious impact on the October election results,” the document said.
Cybersecurity experts also dismissed the claims.
“Some points are old complaints,” said Diego Aranha, a Brazilian computer scientist who has studied the election system. “Others are completely fabricated.”