The sweeping probe ordered by Justice Luiz Edson Fachin encompassed all the likely presidential candidates from Brazil's main political parties, including left-leaning former President Luiz Inácio Lula da Silva who is leading in the polls.

"A chance for a clean start," O Globo, an influential Rio de Janeiro daily, said on Wednesday's front page.

But many familiar with the workings of Brazil's multiparty system and its sluggish courts said the investigation may bring little beyond more instability - especially if an untested maverick steps in to fill the political void.

"It's good we have institutions that are battling corruption but this opens up a gaping leadership vacuum that for now creates further instability," said Rafael Cortez, a political scientist at Tendencias, a consultancy in São Paulo.

The massive investigation that opened three years ago into kickbacks at the state run oil company Petrobras has already shaken Brazil's political establishment. It contributed to the impeachment of leftist President Dilma Rousseff last year, and has dogged the new government of President Michel Temer.

Yet the investigation ordered by Fachin on Tuesday, based on plea bargain testimony by employees of engineering company Odebrecht, marked a major escalation of the political fallout.

Eight government ministers and 12 state governors were swept up in the probe, as well as dozens of sitting lawmakers - including the speakers of both houses of Congress - and four former presidents.

After emptying out Tuesday afternoon when the probes were announced, Congress remained largely vacant on Wednesday as nervous lawmakers weighed the repercussions.

SKEPTICAL OF CHANGE

The investigations were welcomed by many citizens in a country wearied by daily reports of corruption and in dire need of political progress to revive an economy saddled by two years of recession.

"I would like to see new leadership, a new electoral option," said Jurandir Ferreira dos Santos, 32, an administrative assistant in São Paulo.

Like many Brazilians, he was skeptical about the political class' ability to change. "We are seeing no one emerging in Congress to provide leadership, no new parties capable of offering us an option we can believe in."

On a practical level, the popular mood may force major political parties to rethink the political calculus behind the various possible candidates.

The center-right Brazilian Social Democratic Party (PSDB) saw two of its possible choices, senators Aécio Neves and José Serra, named in Fachin's probe. A third possible PSDB contender, São Paulo Governor Geraldo Alckmin, was referred by Fachin for investigation by a lower court.

Some politicians portrayed the investigations as a welcome chance to clear their names. Neves, who lost the 2014 election to Rousseff, said in a statement it would now be possible to "unmask the lies and show the absolute propriety" of his conduct.

With an antsy electorate, though, the uncertainty could open the door to newcomers casting themselves as agents of change.

PSDB members are already speculating whether João Doria, a wealthy businessman and upstart politician who surprised rivals by getting elected mayor of Sao Paulo last year, may be the party's only untainted option.

There could also be an opportunity for brazen populists like Jair Bolsonaro, a renegade conservative who espouses a nationalist, law-and-order agenda and has stirred controversy with his views on gender and race.

"You never know who might take advantage of the electoral mess," says Carlos Melo, a professor of politics at Insper, a São Paulo business school. "An outsider might make the best president ever or maybe they'd be the worst."