In an article previous year calling him "Brazil's Donald Trump", The Economistdescribed Bolsonaro as a "religious nationalist and former army captain, he is anti-gay, pro-gun, and an apologist for dictators who tortured and killed Brazilians between 1964 and 1985". He was rushed to an area hospital where his son said he is being treated for non-life threatening injuries. If Bolsonaro is not able to go out in the streets, it could jeopardize his campaign. A medical team is evaluating whether Mr Bolsonaro can be transferred to another hospital in Sao Paulo. The candidate appears to grimace, then double over in pain.
A suspect identified as 40-year-old Adélio Bispo de Oliveira was arrested on the scene, police confirmed.
According to diario26.com, Oliveira is an "activist" who was affiliated with the Socialism and Freedom Party (PSOL) in Minas Gerais between 2007 and 2014.
The incident comes amid a tumultuous period in Brazil's history that has seen a sweeping corruption investigation roil the political establishment and inflame Brazilian citizens still suffering after a devastating, two-year recession. He opposes abortion and same-sex marriage and has compared himself to U.S. President Donald Trump.
His statements about women, minorities and LGBT (lesbian, gay, bisexual and transgender) people have repelled some Brazilians, but attracted many others who support his free-market policies and hard-line law-and-order stance.
Bolsonaro, a former army captain, is second in the polls to jailed ex-President Luiz Inacio Lula da Silva, who has been barred from running but continues to appeal. Both Silva and Gomes trailed Bolsonaro in the polls with 12 percent each.
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The only Brazilian politician now more popular is the leftist ex-president Luiz Inacio Lula da Silva, who is in prison for corruption and has been banned from competing in October's election. Bolsonaro in recent weeks had taken to campaigning with a bulletproof vest.
"Our agents there said the attacker said he was 'on a mission from God, '" said Luis Boudens, president of the National Federation of Federal Police.
The attack on Bolsonaro, 63, is a dramatic twist in what was already Brazil's most unpredictable election since the country's return to democracy three decades ago. He says the attack will only help his father electorally.
The benchmark Ibovespa stock index climbed 1.8 per cent on Thursday.
"We do not know if it was politically motivated", said Cpl.
Jair Bolsonaro is now undergoing surgery, BBC reported, after his liver was injured in the stabbing. The attack ocurred as the candidate was moving slowly through a large crowd.