BRASILIA (Reuters) - The jailing of Brazil’s former President Luiz Inacio Lula da Silva has hardened convictions in his Workers Party that he should be nominated to run for president, its senior members said, a plan that may leave the broader left fragmented as elections approach.

A flag with the image of former Brazilian President Luiz Inacio Lula da Silva is seen during a protest in support of Lula, in Buenos Aires, Argentina, April 11, 2018.

There is little chance Lula, convicted of bribery and facing six more graft trials, will be eligible to stand for the October vote, even if freed by an appeal that the Supreme Court could take up on Wednesday.

But the Workers Party has closed ranks behind him, with the national executive saying on Monday that they will register him as a presidential candidate close to the August deadline for hopefuls to enter the race. That delays the chance for an electoral court to formally bar his candidacy and keeps pressure on the judiciary for locking up the campaign front-runner.

Even party officials who previously backed at least discussing alternative candidates after Lula’s conviction last year now say it is no time for such debate.

“To talk about Plan B now would divide the party at a moment when our tactic is to strengthen Lula,” said Washington Quaqua, the head of the Workers Party in Rio de Janeiro state. “He is our candidate until he decides otherwise. We will take this to the limit.”

A party official said Lula’s sudden imprisonment after losing a Supreme Court ruling last week left leaders in a state of shock, turning their focus to a vigil outside of the police headquarters in the southern city of Curitiba where he is held.

“They are all still stunned and nobody can discuss clearly what the best options are,” said the official, who works in the party leadership in Brasilia but asked not to be named because he was not authorized to speak publicly about the situation.

LULA’S POLITICAL CAPITAL

Keeping Lula as a candidate is a way to maximize the eventual transfer of his political capital to an heir he has so far avoided publicly choosing, according to political scientist Rubens Figueiredo.

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But Figueiredo said the strategy risks hurting the left’s electoral odds by delaying the campaign of a successor until it is too late.

“Lula’s plan is to continue on the political stage as long as he can. And when he is barred he will say: ‘Since I can’t, here is my candidate,’” said Figueiredo, director of Sao Paulo research center CEPAC.

Parties can change their candidate on the ballot until 20 days before the Oct. 7 election. Opinion polls before his imprisonment showed Lula well ahead of other potential candidates, with 36 percent of voter intentions in the most recent Datafolha survey in January.

Lula’s most likely chosen heir is former Sao Paulo Mayor Fernando Haddad, who has a limited national profile and is polling in the low single digits, but has not been caught up in the graft investigations that have swept Brazil’s political class and disgusted voters.

Another option is former Bahia Governor Jaques Wagner, who has dropped out of public sight in recent months. Police are investigating him over accusations of bribery, related to the building of a World Cup soccer stadium in his state.

Senator Gleisi Hoffmann, the current leader of the Workers Party and a fiery speaker who Lula chose as his spokeswoman, also has legal woes.

The Supreme Court ruled in 2016 that she must stand trial for allegedly receiving 1 million reais ($290,000) in illegal funds for her 2010 Senate campaign.

Wagner, Hoffman and Lula have denied committing any crimes.

The dominance of the Workers Party over the past two decades - and Lula’s importance within the party - has given little room on the left for other standard bearers who could fill his shoes.

Polls show former Ceara state governor Ciro Gomes, running for the populist Democratic Labor Party, and environmentalist Marina Silva would each draw about 15 percent of his votes.

But the other 70 percent remains up for grabs, between otherwise undecided voters and disenchanted Lula supporters, some of whom have told pollsters they intend to cast null or blank votes.