Former Brazilian President Luis Inacio Lula da Silva has been nominated to run for office again in October's elections despite currently being in jail on a 12-year sentence for corruption.
Some 2,000 members of his Workers Party declared him their candidate by a show of hands in Sao Paulo.
Lula leads most opinion polls but may not be allowed to stand.
He has denied taking bribes and says his conviction is part of a plot to prevent him returning to power.
A message from the former leader was read to party members, many wearing Lula masks, who had gathered for a convention in Brazil's main city.
"They want to scrap the people's right to choose the president," the message said, quoted by AFP.
"They want to create a democracy without the people. We have an enormous responsibility ahead."
The party is not expected to name Lula's running mate until Monday.
The appointment is important as the vice-presidential choice could potentially be elected president if Lula is not allowed to stand.
Polls suggest Lula has almost double the support of his nearest rivals.
Two other candidates were also nominated on Saturday - Marina Silva by the centre-left Rede party and Geraldo Alckmin by the centre-right Social Democracy Party.
Lula was convicted of receiving a renovated beachfront apartment worth some 3.7m reais ($1.1m; £790,000) as a bribe by engineering firm OAS.
The defence says his ownership of the apartment has never been proven and that his conviction rests largely on the word of the former chairman of OAS, himself convicted of corruption.
Lula lost his first appeal in January, when the appeals court not only upheld his conviction but increased the sentence from nine-and-a-half years to 12.
He is still waiting for a final court judgement on whether he can run, but under current law someone who loses an appeal against a criminal conviction cannot stand for the presidency.