A widening corruption probe has turned key lawmakers from Brazil's largest party against leftist President Dilma Rousseff, threatening to split her coalition and increasing chances of her impeachment in Congress this year.
The Brazilian Democratic Movement Party, known as the PMDB, is the main ally of the ruling Workers' Party. Its leader, Michel Temer, is Rousseff's vice president.
But, a growing number of legislators from the fractious party, which accommodates centrist and centre-right politicians, say it is time to abandon a president they see as paralysed by political gridlock and unable to lead Brazil out of an intense economic recession.
"This is a very delicate moment," said the party's Vice-President, Senator Valdir Raupp, who no longer wants to support Rousseff's coalition. "The country needs a change of course now."
What little patience some PMDB lawmakers still had for the coalition has frayed amid an investigation into the ruling party's founder, former president Luiz Inacio Lula da Silva, and new allegations money from a far-reaching corruption scandal helped fund Rousseff's 2014 re-election.
At its biennial convention Saturday, the PMDB will loosen its alliance with the administration, which has been roiled by the ongoing kickback scandal around state-run oil company Petroleo Brasileiro SA.
While avoiding an outright break with Rousseff, PMDB officials say they will vote on measures intended to give individual party lawmakers more freedom to rebel against Rousseff initiatives and ultimately vote in favour of ousting the president, who faces impeachment proceedings because of accounting irregularities in the government budget.
If PMDB legislators do end up voting to impeach Rousseff, one benefit for the party, which plans to field its own candidate in the 2018 presidential election, is that Temer would become president.
Rousseff has denied any wrongdoing and dismissed the impeachment efforts as baseless.
PMDB support for an immediate departure from Rousseff's coalition could gather more force if there is a massive turnout in a nationwide protest for Rousseff's impeachment called for Sunday by opposition parties.
"The streets of Brazil will be decisive," said Perondi, the PMDB Congressman.