“HE HAS principles and convictions,” read the citation for Demóstenes Torres in Época's list of the 100 most influential Brazilians of 2009. The senator from the state of Goiás, continued the magazine, was “not just another trafficker of political influence”.

Around the same time, police investigating illegal gambling were wiretapping Carlos Augusto Ramos (known as Carlinhos Cachoeira or “Charlie Waterfall”), a businessman thought to have ties to Brazil's renowned numbers racket, the jogo do bicho (animal game; see article). Among his frequent callers was Mr Torres, who chatted about planned laws and projects, and asked for money. Mr Torres insists Mr Cachoeira is just a close friend. So he will presumably visit Mr Cachoeira in jail, where he is being held on suspicion of money-laundering, corruption and running an illegal gambling network.

Scandals are par for the course in Brasília, but this one promises to spray unusual amounts of muck. On April 25th Congress launched an inquiry into Mr Cachoeira's political influence. It has convened an investigative committee that can look into or summon to testify anyone it wants, and has access to confidential bank, tax and phone records. So far it has named three federal deputies and two governors (as well as Mr Torres) as subjects of interest. It also plans to investigate Delta, a big Brazilian construction firm. One of the company's former managers is now in jail after appearing in the wiretaps.

Lawyers for politicians who showed up on the tapes are trying to get the evidence declared inadmissible—precisely because of their clients' closeness to Mr Cachoeira. They argue that since holders of high office in Brazil can only be investigated by their peers, the police should have backed off as soon as they saw that Mr Cachoeira's list of regular callers read like a political “Who's Who”. Police retort that politicians were peripheral to their main investigation, and that they told the attorney-general, Roberto Gurgel, about the political angle three years ago. The committee is planning to invite Mr Gurgel to explain why he did nothing until the wiretaps were leaked to the press.

Whatever the legal arguments, dropping the inquiry would probably cause too much public ire to be feasible. For now, the political costs of the investigation look likely to fall on the opposition to the centre-left government of Dilma Rousseff. Mr Torres was affiliated with the Democrats, a conservative party that had already been weakened by defections. His public shaming may hinder their rumoured plan to merge with the biggest opposition party.

But the revelations are not necessarily a political gift for Ms Rousseff. Although the hard line she has taken on corruption since becoming president should give her a reserve of credibility with the public, congressional inquiries are highly unpredictable. Her aides are particularly concerned about Luiz Antonio Pagot, a former senior transport official who resigned last year after being accused of corruption. He now says he was forced out to suit Mr Cachoeira and Delta. Sérgio Cabral, the governor of Rio de Janeiro state and a close ally of Ms Rousseff, may also face awkward questions: he is a good friend of Fernando Cavendish, a former boss of Delta, who had to step down once the scandal broke.

Even if Ms Rousseff emerges politically unscathed, the investigation will probably hinder some of her plans. There is little hope of passing urgent legislative business, such as a long-stalled deal on sharing proceeds from deep-sea oil drilling between states, while politicians gossip, plot and counter-plot. And much-needed infrastructure projects—particularly in preparation for the 2014 football World Cup and 2016 Olympics in Rio de Janeiro—could be slowed by the examination of Delta's many federal contracts for possible corruption or over-billing. Many are already over budget and behind schedule. Its partners in the consortium rebuilding the Maracanã stadium, the venue for the World Cup final, have already expelled it and say they will continue on their own. Their promise to finish on time seems optimistic.

Pedro Taques, a former prosecutor who is now on the investigative committee, says the outing of Mr Torres proves not that graft is growing but rather that anti-corruption efforts are getting better. Even so, the more the rot in Brazilian politics is exposed, the fewer politicians citizens will feel they can trust. Sylvio Costa of Congresso em Foco, a prize-winning investigative magazine, worries voters will simply give up on all of them. “That it's Demóstenes, of all people,” he says, “is poisonous for political engagement.”