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Brazil's Supreme Court began deliberations Thursday in a case involving a cash-for-votes scheme in the legislature that could tarnish the legacy of hugely popular former President Luis Inacio Lula da Silva and the ruling party.

Despite dredging up details of what some call the largest political corruption case in Brazil's history, the Supreme Court trial is also being hailed as a sign of political health in a country where public service has long been marred by corruption and impunity.

"It's a change of game. Brazilians are going to see someone accused of corruption really go to trial, maybe get convicted. Impunity no longer operates," said David Fleischer, a political scientist at the University of Brasilia. "This is going to turn a page. In the future, politicians will be very careful, much more cautious about how they do things."

The main defendant is Jose Dirceu, a former chief of staff for Silva, who left office with an 87 percent approval rate. It also involves 37 other members of the ruling Workers' Party. Silva himself is not accused of any wrongdoings.

The accusations revolve around Dirceu, one of the party's founders, who is accused of orchestrating regular bribes to legislators from allied parties to secure their votes after the Workers' Party came to power in 2003. The case is known in Brazil as "mensalao," or big monthly allowance, for the sums of up to $10,000 allegedly handed over to politicians.

Dirceu is entitled to a hearing before the highest court because of his political rank. The Supreme Court judges decided to package all 38 defendants together into one 50,000-page case involving 600 witnesses because of the interconnected nature of the 1,089 charges, which include corruption, money-laundering, misuse of public funds, embezzlement and conspiracy.

Dirceu's attorneys said in a written statement that they have given the judges arguments that invalidate all the accusations against their client. What did happen, the attorneys said, was some off-the-books accounting for which the former party treasurer and the Workers' Party assumed responsibility.

"The government never intervened nor had any knowledge of such financial-electoral agreements," their statement said, referring to Silva's administration.

Attorney General Roberto Gurgel described the case as "the most daring and outrageous corruption scheme and embezzlement of public funds ever seen in Brazil," according to his last official statement before the start of trial.

Silva himself came under question when he met with Supreme Court judge Gilmar Mendes in May. The justice told local media that Silva requested a postponement of the trial until after the October municipal elections to help the Workers' Party at the polls. Silva confirmed they'd met, but denied the political allegation.

The former president made a show of his lack of interest in the case, attending a business event in Sao Paulo hours before the trial started. Asked if he was going to follow the television broadcast of the proceedings, he said, "I have more things to do, the lawyers are the ones who need to watch."

So far, though the case has had few repercussions for Silva and his anointed successor, President Dilma Rousseff.

Dirceu and other Silva aides resigned once allegations surfaced in 2005, saying they were innocent. They haven't held significant office since, although several have had lucrative consulting careers.

Silva was re-elected after the scandal broke, and still had enough pull at the end of his second term to help elect Rousseff. He's beloved still for funding transfer of wealth programs that helped lift millions of Brazilians out of poverty.

After Dirceu fell, Rousseff was tapped to substitute him as chief of staff. Since she won the presidency in 2010, Rousseff has developed a reputation for zero tolerance toward political malfeasance after pushing out seven ministers in her first year following corruption allegations.

Still, Brazilians are riveted by the trial and the prospect of real punishment for the wealthy and powerful, something almost unheard of here.

Paulo Maluf has faced allegations of corruption since the 1980s and is now on an Interpol wanted list after being charged in the United States with theft connected to a bribery scheme. He is now a congressman. Fernando Collor, a former president who resigned to avoid impeachment in a corruption scandal, is now a senator. His father, Arnon de Mello, shot and killed a fellow senator in the 1960s, but was never tried.

Seen against this backdrop, some analysts say the case is a beacon of hope for a better Brazil.

"It's emblematic because it is, finally, that long-awaited response to society. It's that case that takes these powerful people to justice," said Leo Torresan of Amarribo, a Brazilian nonprofit partnered with Transparency International working for openness in government.

The trial isn't the only recent sign of progress. Over the past years, including Silva's two terms in office, important measures were taken to strengthen institutions and fight graft.

Government accounting bodies were given free rein to examine use of public funds. An external control body for the judiciary was created in 2004, and it has gone after judges accused of committing crimes.

Local news media have become more aggressive in exposing corruption and a recently approved freedom of information law will make it easier for reporters and members of the public to investigate politicians.

A measure in Congress to end secret voting has already been approved in the Senate, and might be approved in the House by the end of the year, Fleischer said.

Finally, an anti-corruption law born of a petition signed by more than a million Brazilians will be put to work for the first time in the upcoming October municipal elections. The law, called "clean slate," forbids politicians who were impeached or convicted from running for office for eight years. It also covers those who renounced office to avoid impeachment.

But Joao Augusto de Castro Neves, a Latin America analyst for the Eurasia Group, a political risk consultancy, said much depends on the outcome of the trial.

"We've got this World Cup final atmosphere. All everyone talks about is 'mensalao,'" said Castro Neves. "The symbolism is huge. For a country where politicians could kill and not be arrested, this trial is positive, period. But on its own, it isn't enough. We have to see how well the trial will be carried out."

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Follow Juliana Barbassa at http://twitter.com/jbarbassa