Jair Bolsonaro, a far-right candidate in Brazil's upcoming presidential election, suffered a knife attack on Thursday, during a campaign rally in the southern city of Juiz de Fora.
A woman lights a candle for presidential candidate Jair Bolsonaro after he was stabbed by a man in Juiz de Fora at Paulista avenue in Sao Paulo, Brazil September 6, 2018.
With jailed former president Luiz Inacio Lula da Silva ruled out of the October 7 election, the latest polls from the Ibope Institute put Bolsonaro in a clear lead with 22 percent compared with 12 percent each for environmentalist Marina Silva and centre-left runner Ciro Gomes.
Lula has however been barred from participating by the Supreme Court which disqualified him on Thursday.
Video footage showed Bolsonaro atop supporters' shoulders, clutching his stomach and grimacing after the assault.
Police told the Associated Press that they have a suspect in custody.
Military police have arrested a suspect who had to be rescued after angry crowds tried to lynch him - he has been identified as Adélio Bispo de Oliveira.
After his arrest, Mr Bispo de Oliveira said he was "carrying out a divine mission, a mission from God", said Luis Boundens, head of a union of federal police officers.More news: Protesters dressed in ‘Handmaid’s Tale’ costumes are waiting outside the Kavanaugh hearing
One supporter, Bruno Engler, 21, who is running for a Minas Gerais state congressional seat on Bolsonaro's Social Liberal Party, said if he could, he would lynch the suspect.
His son Flavio Bolsonaro confirmed his father's injuries are serious, saying "the perforation reached part of the liver, the lung and the intestine loop". Supporters outside the hospital carried a giant inflatable doll of Bolsonaro dressed in a formal suit with a sash that said "President".
But Flavio Bolsonaro, the candidate's son, said early Friday outside the hospital where his father was treated that he was conscious and the attack was a political boost.
"It's likely that Bolsonaro will use the attack to argue his opponents are desperate, that they had no other way to stop him", said Mauricio Santoro, a political science professor at Rio de Janeiro's state university.
The stabbing of a leading Brazilian presidential candidate has the potential to reshape the election contest after dramatically exposing the deep polarisation in Latin America's largest nation.
In many ways, the incident feeds Mr Bolsonaro's narrative that Brazil is in chaos and needs a strong hand to steady it.
Despite being a long-serving member of Congress, Bolsonaro has successfully presented himself as an outsider, untouched by the corruption scandals engulfing so much of the political elite.
Lula, who was previously leading the opinion polls, is now serving a 12-year prison sentence for fraud related to a corruption scandal.