Brazilians will vote on Sunday in a polarised presidential race that could result in the election of a far-right former Army captain, whose praise of past dictatorships enrages critics but whose promise of a brutal crackdown on crime and corruption has electrified his supporters.
With 68 percent of voters counted, Bolsonaro had received 46 percent of valid votes, far ahead of Haddad's 25 percent.
On Oct. 28, Bolsonaro will face second-place finisher Fernando Haddad in a runoff vote. In the weeks ahead of an October 28 runoff against former Sao Paulo mayor Fernando Haddad, Bolsonaro's main proposals are sure to come under much scrutiny. A runoff is required under Brazilian law if no candidate wins a majority. Bolsonaro has often praised Trump, and his campaign took many pages from the US president's playbook, from bashing the mainstream media and political class to using the candidate's adult children as proxies.
Dubbed a "Tropical Trump" by some pundits because of his nationalist agenda and anti-establishment tirades, Bolsonaro was swept from the political margins this year by a wave of antipathy toward scandal-plagued traditional parties.
Still, preliminary results showed unexpectedly big congressional wins by Bolsonaro proxies including former military police Major Olimpio Gomes, his campaign manager in Sao Paulo, who was elected to Senate.
Senna said he was anxious that Bolsonaro's presidential rivals would gang up on him and back Haddad in the runoff.
Haddad can only win in the second round if he converts sceptics, galvanises Sunday's vanquished centrist candidates and their supporters and goes after his opponent on policy issues such as crime and security which, until now, he has appeared unwilling to grapple with, analysts said.
"This was a great victory, considering we had no television time, a party that is still very small with no campaign money and I was in hospital for 30 days", he said in video streamed live over social media.
Bolsonaro, whose campaign was called "Brazil above all, God above everyone", has pushed a nostalgic narrative that he can bring back better times.
"Haddad's chance of victory depends much more on the performance of Bolsonaro than his own".
Better-off Brazilians have rallied to Bolsonaro's pledge to crush crime that includes more than 62,000 murders each year, almost as many rapes and frequent robberies.
Prior to Sunday's first-round vote, about 41 percent of Brazil's electorate said they wouldn't vote for Haddad under any circumstances, according to Datafolha polling institute.
Many voters also like his promises to tackle corruption and to cut climbing public debt through privatizations, as well as the devout Catholic's family-first stance. Haddad - a stand-in for jailed former president Luiz Inácio Lula da Silva, who's now serving 12 years for corruption - trailed Bolsonaro with 29 percent.
Congressman Onyx Lorenzoni, the main political advisor to Bolsonaro, said his team was targeting individual lawmakers in parties opposed to the PT, including those in parties whose leaders do not yet support the right-winger.