Those assertions resonated with supporters of Mr. Bolsonaro as he faced a tight runoff on Sunday for the presidency against the once-imprisoned former President Luiz Inácio Lula da Silva.

In recent weeks, however, Mr. Bolsonaro worried about the prospect of prison himself, according to two senior officials who heard those concerns from the president and spoke anonymously to describe private conversations.

Despite his assertions, Mr. Bolsonaro and his inner circle have faced investigations on accusations including the embezzlement of public funds, theft of staff wages and mishandling of the Covid-19 pandemic. The inquiries had been staved off or blocked so far, given his political influence and presidential immunity.