SAO PAULO (Reuters) - Brazilian voters are abandoning jailed former President Luiz Inacio Lula da Silva as his chances of running in October fade, but they are not transferring their support en masse to other leftist candidates, a Datafolha poll showed on Sunday.

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Without Lula in the running, support for far-right candidate Jair Bolsonaro has slipped and is now virtually tied with environmentalist Marina Silva in a presidential race thrown wide open, the survey said.

The wild card in the election now appears to be former Chief Justice Joaquim Barbosa, a popular figure due to his anti-corruption record who has jumped into third place in his first showing since he joined a party eyeing a presidential bid.

The first poll since Lula started serving a 12-year prison sentence last week for taking bribes showed he would still lead the race with 31 percent of voter intentions, down from 37 percent in the previous Datafolha survey in January.

Bolsonaro, a former army captain who was charged with racism on Friday for inciting hatred with racist statements and could face up to three years in prison, has 17 percent of voter support, down from a peak of 21 percent in November.

Barbosa, the first black member of Brazil’s Supreme Court who handled a vote-buying trial that led to the jailing of several of Lula’s closest aides in 2012, has between 9 percent and 10 percent voter support, Datafolha found.

Ciro Gomes, the leftist former governor of Ceará state who was expected to draw Lula voters, slipped to 9 percent from 12 percent in January, and Lula’s likely replacement as candidate for his Workers Party, former Sao Paulo Mayor Fernando Haddad has just 2 percent, the poll said.

Other leftist candidates close to Lula, Guilherme Boulos of the Socialism and Liberty Party and Manuela D’Avila of the Communist Party of Brazil have not gained ground at all, with 1 and 2 percent respectively.

Lula is unlikely to be a candidate because Brazilian laws bar anyone convicted of a crime from being eligible for elected office for eight years. His party’s plan to register his candidacy anyway is expected to be rejected by the top electoral court.

While Brazilians are split on whether Lula should be allowed to run, 62 percent believe he will be barred, the poll said.

Support for the strongest candidate among Brazil’s major centrist parties, former Sao Paulo Governor Geraldo Alckmin of the Brazilian Social Democracy Party, is stagnant at between 7 and 8 percent, while the ruling Brazilian Democratic Movement (MDB) party’s hopefuls fare even worse.

President Michel Temer, who has said he wants to run in October, has between 1 percent and 2 percent, while former Finance Minister Henrique Meirelles has not cleared 1 percent. Both are affiliated with the MDB.

Datafolha surveyed 4,194 adults across Brazil between April 11-13. The poll has a margin of error of 2 percentage points.