Other steps Lula has taken to shore up support before the runoff include cutting fuel taxes, pardoning the government debts of 3.6 million small businesses, moving to block cellphone signals around prisons, and proposing to boost welfare payments to university students. He has also repeatedly warned the US not to meddle in Brazil’s elections and has made defending Brazil's sovereignty a key campaign issue.
Brazilians cast ballots using electronic voting machines, punching in digits that correspond to their candidates in a tense presidential run-off campaign that feels like a psychological thriller. Joining Lula and Bolsonaro on runoff ballots are governors in five states and the federal district, while people who missed the first round can vote in the second.
Brazil plays a vital role in mitigating global warming by protecting the Amazon rainforest, but deforestation hit a record high during Bolsonaro's presidency, and his son has likewise denied human-caused climate change, committing only to stopping illegal deforestation.
Bolsonaro's supporters were jubilant at his final campaign rallies, confident that he would bring change to Brazil through his promised tough crackdown on organised crime, as well as tax and public spending cuts.
Bolsonaro bested Lula by more than 2.2 million votes in the first round of the election held earlier this month, but neither candidate secured an absolute majority, leading to Sunday's runoff.
Read moreBrazil's tense presidential run-off campaign feels like a psychological thriller Other steps Lula has taken to shore up support before the runoff include cutting fuel taxes, pardoning the government debts of 3.6 million small businesses, moving to block cellphone signals around prisons, and proposing to boost welfare payments to university students.
Since Bolsonaro's first-round victory, supporters of Lula have arranged huge rallies in support of him to try to boost turnout after 33 million people did not cast a vote earlier this month.
But more than 33 million, or 21 percent of the electorate, did not vote earlier this month, and could face a small fine for failing to cast a ballot without justification.