Key parties in Brazilian President Michel Temer's ruling coalition were expected to decide Sunday whether to remain loyal as leftist groups protested and an influential lawyers' group called for his impeachment.
The center-right president is being probed for allegedly obstructing a corruption investigation by paying hush money to jailed former speaker of the house Eduardo Cunha.
On Sunday, Temer fought back, saying that a secret audio recording incriminating him had been tampered with. His demand for the probe to be suspended will be examined by the Supreme Court on Wednesday.
But Temer -- who took over only a year ago after the impeachment of leftist president Dilma Rousseff -- already faces growing calls for his resignation and new elections.
Brazil's bar association, the Order of Brazilian Lawyers, voted overwhelmingly late Saturday to lodge an impeachment request with Congress, adding to at least eight already filed. The association was also influential in the impeachment of Rousseff last year.
Meanwhile, leftist groups held small demonstrations Sunday in the capital Brasilia and Rio de Janeiro. More protests were planned later in Sao Paulo.
The left, long angered by Temer's role in engineering the impeachment of Rousseff and his subsequent attempt to push through economic austerity reforms, has seized on the sudden corruption scandal as an opportunity for payback.
"This is the result of the coup against President Dilma," said Mario Vitorio, a 55-year-old public servant, at the Brasilia protest. "We want Temer out, direct elections and an end to the reforms."
Temer took over automatically from Rousseff without an election and his reforms package -- praised by economists and investors, but hated by ordinary Brazilians -- has made him hugely unpopular.
That leaves his only power base the alliance in Congress between his center-right PMDB party and numerous partners. Since the scandal over his alleged obstruction of justice, support has been bleeding away in the coalition.
Late Sunday the main partner -- the PSDB social democrats -- was meeting to decide whether to break with Temer. The smaller DEM and PPS parties were reportedly to join in an effort to reach a common position.
The PSB party, with one minister in the government, quit Saturday.
Defection by the PSDB would present a blow of a more serious nature to Temer, weakening his chances of avoiding impeachment. The PSDB has four ministers and with 47 lower house deputies and 10 senators represents an important pro-government voting bloc.
If Temer were impeached or decided to step down, Congress would pick a replacement to rule until after scheduled 2018 elections.
However, there is widespread demand among ordinary Brazilians on both the left and right for changing the law to allow a snap popular election.
Temer's crisis is connected to the gigantic corruption investigation know as "Car Wash" that has upended Brazilian politics.
Scores of politicians have been indicted or subjected to probes into alleged bribe-taking and embezzlement, with Temer only the latest to be pulled into the maelstrom.
At the heart of his problems is the conversation he had with an executive from the JBS meat-packing business in which the president allegedly blesses monthly payments of hush money to Cunha.
Temer says he never paid hush money and says the secret recording of his conversation with the executive was misinterpreted, and that the recording itself has been distorted.