Former chief justice and the first black member of Brazil’s Supreme Court, Joaquim Barbosa, joined the centre-left Brazilian Socialist Party (PSB) late on Friday mulling a presidential bid in the October election.

Barbosa, 63, has never run for office but he is widely admired for heading a high-profile 2012 political corruption trial over vote-buying that led to the imprisonment of three top aides to former leftist president Luiz Inacio Lula da Silva.

Since Barbosa retired from the top court in 2014 his name has regularly appeared in presidential opinion polls and he could shake up the election campaign by becoming the anti-establishment candidate many voters are looking for.

“My talks with the PSB have led to an understanding that allows me the comfort of having more time to reflect on a final decision on running,” Barbosa said in a statement. He said the PSB had not guaranteed him the nomination.

PSB officials said their polling shows Barbosa could pick up many of the votes of Brazilians who will abandon Lula’s Workers Party due to his corruption conviction and imminent imprisonment.

A majority of party members favour nominating Barbosa at a convention in June, they said.

With Brazil’s political establishment rocked by political corruption scandals, voters are seeking alternative candidates like Barbosa who are honest and trustworthy, party leader Carlos Siqueira told Reuters last week.

“Barbosa could well be the ‘sleeper’ of this election,” the Eurasia political risk consultancy said in a note to clients.

Barbosa’s anti-corruption credentials will help him draw votes away from centrist candidate Geraldo Alckmin of the Brazilian Social Democracy Party (PSDB) and environmentalist Marina Silva and help him reach the second-round run-off, Eurasia said.