Support has poured in from foreign leftist leaders. Among them are former Presidents Michelle Bachelet of Chile and François Hollande of France as well as the Bolivian leader Evo Morales and 29 United States lawmakers, including Senator Bernie Sanders, who concluded in a letter, “The facts of President Lula’s case give us reason to believe that the main objective of his jailing is to prevent him from running in upcoming elections.”

Mr. da Silva was arrested in April after a dramatic standoff with the police, during which he declared: “I won’t be stopped because I am not a human being, I am an idea. And going forward all of you will become Lulas.”

As part of their Lula-or-bust strategy, several leading members of the Workers’ Party changed their names on social media accounts after he was jailed, adding Lula to their handles. Ms. Hoffmann was among them.

“The judiciary, the elite, the media, they have done everything to try and impede him,” Ms. Hoffmann said. “They thought the only way to stop Lula was to physically remove him, to put him in jail. But far from stopping him, it has just made people more supportive.”

Mr. da Silva, who faces several other corruption charges, leads electoral polls by a wide margin, with 30 percent of Brazilians saying they would vote for him. Perhaps more important, 47 percent say they would “certainly” or “perhaps” vote for a candidate he endorses, according to a recent survey by Datafolha.

That is an impressive showing for someone who has not made a public appearance since April, who can’t record videos, grant interviews to journalists or weigh in on Twitter in real time — although the party updates his social media accounts frequently.