But there is another factor that could have a huge impact on what is becoming the most unpredictable election since the military dictatorship ended in the 1980s: Mr. da Silva.
After two terms, Mr. da Silva left office with an approval rating of 87 percent and even now, sitting behind bars, 30 percent of Brazilians say they would vote for him. His party insists that Mr. da Silva will be its candidate, but his candidacy is likely to be barred by the Supreme Electoral Court later this year. If he chooses to anoint a successor, his decision could tilt the race in his candidate’s favor, especially with Mr. Barbosa out of the race.
Political analysts say Ciro Gomes, the candidate of the leftist Democratic Workers Party, could eventually form an alliance with Mr. da Silva’s Workers’ Party, but so far he is trailing in the polls.
Juliete Araujo, a 24-year-old house cleaner from the impoverished northeast, said it was hard to trust politicians other than Mr. da Silva, who is widely known as Lula.
“Lula is the only one who has ever cared about us,” Ms. Araujo said. “Maybe I would have voted for Joaquim Barbosa, but now if Lula isn’t in the elections, I’ll just cast a blank ballot.”