Six of the eight justices who voted found Jose Dirceu guilty of "active corruption" by organizing the scheme to buy congressional support for Silva's policies through regular payments to legislators in exchange for their votes. Two more justices will vote Wednesday, producing a formal verdict, but a majority is all that's needed for conviction.
The case is known in Brazil as "mensalao," or big monthly allowance, for the sums of up to $10,000 handed over to politicians.
Widely seen as the biggest political corruption scandal in Brazil's history, the case has done little to tarnish the reputation enjoyed by Silva, who left office after two 4-year terms on Jan. 1, 2011, with an 87 percent approval rating. Silva, who remains a powerful political force in Brazil, faces no accusations of wrongdoing. A poll by the Datafolha polling institute said earlier this year that 57 percent of Brazilians would like to see Silva return to the presidency in 2014.
Dirceu, a former revolutionary turned federal lawmaker once seen by many as a potential Brazilian president, was an early member of the leftist Workers Party and served as party president from 1995 through 2002, when he was named chief of staff upon Silva becoming Brazil's first working-class leader. In that role Dirceu was the second most-powerful man in Latin America's largest nation before the scandal broke in 2005 and forced him from the Cabinet.
The public prosecutor's office maintained that Dirceu helped both to orchestrate the flow of bribe money as well as to broker deals with lawmakers on the dole.
Dirceu denied involvement in the vote-buying scheme throughout the investigation. His lawyers argued before the top court that the accusations against him were invalid but did acknowledge some off-the-books accounting. They said Dirceu took responsibility for the irregular accounting and insisted Silva's administration had no knowledge of it.
Under Brazilian law, the corruption charges that Dirceu was convicted on carry a sentence of two to 12 years in prison. Dirceu will be sentenced at the end of the proceedings, which are continuing and will see all 37 defendants tried together because of the interconnected nature of the 1,089 counts they collectively face. Those charges include corruption, money-laundering, misuse of public funds, embezzlement and conspiracy.
Other defendants include legislators and their business associates. Twenty-two of them have already been convicted and four have been acquitted.
Tuesday's verdict marked the final fall from grace for Dirceu, who was once considered a top contender to succeed Silva.
He entered politics as president of the leftist National Students Union and resisted Brazil's 1964-85 military dictatorship, which arrested him in 1968. The following year, an anti-regime group kidnapped U.S. Ambassador Charles Elbrick and demanded the release of 15 imprisoned guerrillas, including Dirceu. Soon after arriving in Mexico he traveled to Cuba, where he had plastic surgery to change his looks and underwent guerrilla training.
Dirceu then sneaked back into Brazil and lived covertly, not even revealing his true identity to the woman he married. Only after the government decreed a political amnesty in 1979 did he go public, helping found the Workers Party with Silva, then a leftist labor union leader.
Though Dirceu maintained his innocence throughout, he resigned as Silva's chief of staff and was expelled from congress after allegations surfaced in 2005.
Silva tapped current President Dilma Rousseff to replace Dirceu as his chief of staff.
Rousseff, who had never held elected office before, won the presidency in 2010 after being anointed Silva's chosen successor.
The "mensalao" scandal has not hit Rousseff's reputation. She's seen as being tough on corruption after pushing out seven of her own Cabinet ministers after allegations of various misdeeds arose in the Brazilian press.
Associated Press writer Bradley Brooks in Sao Paulo contributed to this report.