President Temer had until now managed to stay above the fray in the "Car Wash" corruption probe into embezzlement and bribery.
Temer had until now managed to stay above the fray in the "Car Wash" corruption probe into embezzlement and bribery, which is already ensnaring many of Brazil's biggest political names.
But the wave of accusations caught up with him late Wednesday when O Globo, the country's most powerful newspaper, reported the existence of a secretly recorded conversation in which Temer authorizes payment of hush money to a jailed politician.
The conversation was with Joesley Batista, an executive from JBS, the meat packing giant which hit world headlines recently when police accused it of doctoring bad meat and bribing health inspectors.
Batista allegedly discusses making payments to Eduardo Cunha, the former speaker of the lower house, who is in prison after having been convicted of taking millions of dollars in bribes. Cunha would be paid to keep quiet about other "Car Wash" activities.
Temer admits to meeting Batista but says hush money was never discussed.
Temer is a master of the Brazilian capital's political maze.
He came to power last year automatically because he was vice president when the president, Dilma Rousseff, was impeached for masking the government budget hole. Cunha, also from Temer's PMDB party, led the impeachment drive.
During his one year in power, he has brushed aside his unpopularity as an unelected president, relying on solid support in Congress from a broad center-right coalition. The left, which calls his replacement of Rousseff a coup, has been marginalized.
But there were already signs Thursday that Temer's seemingly solid legislative base is shaking.
Coalitions often have little ideological common ground in Brazil. In addition, many lawmakers themselves are running scared from the corruption scandal -- a third of senators are under investigation in the "Car Wash" probe -- and will now look out for their own survival.
"Resignation is the easiest way to resolve this," said Senator Ana Amelia, from the PP, who had supported Rousseff's impeachment last year.
Crucially, a source in the PSDB, the main partner with Temer's PMDB, says that if the Globo report is confirmed they will quit the government.
By midday Thursday, three requests by lawmakers for the impeachment of Temer had been filed. The leftist Workers' Party of Rousseff scents the chance for revenge.
Having taken over in an emergency capacity, Temer is not due to stay in office longer than January 1, 2019, when the winner of scheduled October 2018 elections takes over.
If he resigned or was pushed out in impeachment proceedings, lower house speaker Rodrigo Maia -- one of the many legislators being investigated in the "Car Wash" probe -- would initially take over.
Thirty days later, Congress would then hold indirect elections for a new president to serve out the rest of that term.
Impeachment would be a more drawn-out process, with first the lower house, then the Senate holding a series of votes that could end in forcing the president out.
There has long been popular pressure for direct, snap elections. However, this would require Congress to amend the constitution first.
Temer might still manage to hold on. The contents of the reported recordings have not been published yet and the wily politician may still cut enough deals with allies to keep their loyalty.
But the mood in Brasilia is getting ugly, meaning that even if Temer does somehow survive, his political brand will be damaged.
That would mean more anger in the streets, like a recent attempt to organize a general strike, which ended with violent clashes in Rio de Janeiro and Sao Paulo.
And in Congress, Temer would struggle all the more to get lawmakers to back his already unpopular austerity reforms, especially a bid to raise the minimum retirement age.
Given that Temer's main promise on taking power last year was to stabilize Brazil and ease it out of a two-year recession, his future looks dim.