Efforts to unite the Brazilian left against rightwing presidential frontrunner Jair Bolsonaro have snagged on internal squabbles, making it even harder to close a gap in opinion polls less than two weeks before the runoff election.

The latest poll, released by Ibope late on Monday, showed that Bolsonaro had a commanding lead over leftist rival Fernando Haddad, with 59% of valid votes against 41% for Haddad.

The poll, details of which ran in newspaper Estado de S Paulo on Tuesday, showed Haddad with a higher rate of “rejection” among voters ahead of the 28 October runoff, due in part to dislike of his Workers Party (PT) even among fellow leftists. About 47% of people polled said they would never vote for him, compared with 35% rejecting Bolsonaro.

The bad news for Haddad came as efforts to attract the voters of Ciro Gomes, who came third in the first round of voting on 7 October after a center-left campaign on the Democratic Labor party ticket, devolved into a shouting match at a campaign event on Monday night.

At a rally in the northeastern state of Ceara, which Gomes won in the first vote, his brother and campaign manager Cid Gomes was called upon to formally endorse Haddad.

But Cid Gomes took the opportunity to call for a mea culpa over sprawling graft schemes orchestrated by leaders of the PT. The party’s founder, former president Luiz Inácio Lula da Silva, is doing jail time for a corruption conviction. Videos of the event showed Cid Gomes was met with rowdy boos.

“You’re going to lose the election, and it’s your fault,” Cid Gomes shot back. “You morons! Lula is in prison!“

The PT held the presidency for 13 of the last 15 years and Lula remains beloved by many for his social policies, credited with easing the lives of the poor in one of the world’s most unequal countries.

Haddad, a former PT mayor of São Paulo, has been unable to distance himself from the disdain many Brazilians harbor for the party’s role in corruption schemes revealed by investigators in recent years.

Haddad has struggled to both stand by Lula, whom the PT considers an unjustly convicted political prisoner, and also acknowledge the party’s errors.

Bolsonaro, 63, a seven-term congressman who openly defends Brazil’s 1964-1985 military dictatorship, is pitching himself as the anti-establishment candidate and appealing to voters fed up with political corruption and violent crime.