Much of that focused on the Workers' Party, and many voters cited a desire to root out corruption in their choice of Bolsonaro.
Haddad, who has presented himself as a fiscally responsible moderate, criticized Bolsonaro for skipping televised debates and accused him of wanting to win in the first round to avoid further democratic discussion.
Should Bolsonaro become president, he will have to form legislative alliances.
Bolsonaro: Trump of the Tropics?
For the past thirty years, Congressman Jair Bolsonaro was a fringe extremist in Brazilian politics, known mostly for outlandish, deliberately inflammatory quotes in which he paid homage to the most notorious torturers of the 1964-1985 military regime, constantly heralded the 1964 coup as a "defense of democracy", told a female socialist colleague in Congress that she was too ugly to "deserve" his rape, announced that he'd rather learn that his son died in a auto accident than was gay, and said he conceived a daughter after having four sons only due to a "moment of weakness". Bolsonaro shares the same lack of filter.
In the interview, he said that record crime rates in Brazil were the main concern for Brazilians, including women.
The two men do share some similarities, including their disdain for political correctness and lack of a filter. He also offered an emphatic defense of the country's old military dictatorship.
He's not wrong, but it doesn't end there-Bolsonaro also wants to withdraw Brazil from the Paris Climate Agreement, harshen law enforcement, weaken environmental regulations, make it easier to get guns and is anti-refugee.
Bolsonaro is riding a wave of anger at the establishment over one of the world's largest political graft schemes and rising crime in the country with most murders in the world.
For candidates who don't trust the media, social networks provide the flawless outlet.
Popular with Brazil's powerful evangelical and farming lobby, Bolsonaro has pledged to pull Brazil out of the Paris Agreement climate deal due to disagreements over how the Amazon should be protected.
Bolsonaro has painted a nation in collapse, where drug traffickers and politicians steal with equal impunity, and moral rot has set in.
Bolsonaro has raised the specter of fraud and said it could rob him of the election.
Polls predicted Mr Bolsonaro would come out in front on Sunday, but he far outperformed expectations, blazing past competitors with more financing, institutional backing of parties and free air time on television.
The elections were overshadowed by the worst economic crisis in Brazil's history, with the GDP drop between 2015 and 2016 the largest since the 1929 crash, and the slowest recovery in history, with employment and median income projected by bourgeois economists to return to their 2013 levels only by 2027.
Reflecting confidence that he will win the second round, Bolsonaro said he had already begun talks with other lawmakers in Congress to build an eventual governing coalition.
"These elections are a real chance for us", said Nailma Bispo, a business developer from Ilheus to ABC News.
If elected, Bolsonaro has promised a total overhaul of Brazil's government.
The country's Superior Electoral Tribunal announced the runoff late Sunday after all the votes were counted. However, by then it had surely been seen by millions of people on Twitter and the messaging group WhatsApp. When pressed with questions, he offered up Paulo Guedes, a market-friendly economist he said he would appoint as finance minister to curtail the social spending that grew under the Workers' Party. "Trump or Bolsonaro can always say, 'I didn't or would never say that'".