Brazil’s far-right presidential candidate Jair Bolsonaro, in intensive care after being stabbed at a campaign rally, kept his first-round lead in an election opinion poll on Friday, but a leftist rival from the Workers Party (PT) made solid gains.

Bolsonaro was backed by 26 per cent of those surveyed, up two percentage points from the same poll published earlier this week, according to the Datafolha survey published by the Folha de S.Paulo newspaper.

The knife attack against Bolsonaro last week has further complicated Brazil’s most unpredictable election in three decades, with its most popular politician, jailed former president Luiz Inacio Lula da Silva, banned from running in the Oct. 7 vote due to a corruption conviction.

Lula’s hand-picked successor to stand for the PT is former Sao Paulo mayor Fernando Haddad, who jumped to 13 per cent of support in Friday’s poll, up 4 points.

The poll indicates the PT’s strategy of transferring Lula’s massive appeal to the relatively unknown Haddad is bearing fruit. The party’s campaign rolled out advertising this week with the simple message: “Haddad is Lula.”

Lula’s backing is expected to propel Haddad into a likely Oct. 28 runoff vote, required if no candidate takes a majority in the first ballot. The Datafolha poll showed that Bolsonaro, who has spent nearly three decades in Congress, and Haddad would be technically tied in a simulated second-round vote.

Bolsonaro would lose to all other major candidates in a runoff, the survey found. A former army captain who favours easing gun control laws to fight crime, Bolsonaro has enraged many Brazilians with comments denigrating women, gays, blacks and indigenous people.

He has led the field from the outset in polls that excluded Lula, tapping into voter anger over political corruption. But the polarizing nature of Bolsonaro means he has the highest rejection rate of all contenders, holding even at 44 per cent on Friday. Haddad’s rejection rate is 26 per cent, up 4 percentage points from Monday.

Support for centre-left candidate Ciro Gomes, a former governor of Ceará state in Brazil’s poor northeast, stayed even at 13 per cent. Business-friendly candidate Geraldo Alckmin saw his campaign continue to stagnate, with the poll indicating support of 9 per cent. Environmentalist Marina Silva fell 3 percentage points to 8 per cent.

Datafolha interviewed 2,820 people across Brazil on Thursday and Friday for the survey, which has a 2 percentage point margin of error.