RIO DE JANEIRO — A justice on Brazil’s Supreme Court on Monday night removed the powerful head of the Senate from his post, as tensions have escalated between Congress and the judiciary over efforts by legislators to curb the power of prosecutors and judges overseeing corruption investigations.
The justice, Marco Aurélio Mello, based his ruling on the fact that the Senate leader, Renan Calheiros, is going to stand trial in a graft case in which a lobbyist paid for the child support of a daughter Mr. Calheiros, 61, fathered in an extramarital affair.
Mr. Mello’s ruling reflects how Brazil’s political tumult is intensifying once again, in a year in which President Dilma Rousseff was ousted and an orchestrator of her impeachment, Eduardo Cunha, the former speaker of the lower house, is now in jail on graft charges.
The move by Mr. Mello also comes amid a tense standoff between Congress and the judiciary. Last week, the lower house held a marathon session in which its members gutted a long-awaited anticorruption bill.
The legislation, which would erode the authority of prosecutors and judges guiding graft inquiries, then moved to the Senate, where Mr. Calheiros unsuccessfully tried to hold a vote on it. Thousands of Brazilians took to the streets on Sunday to protest the moves in Congress, venting their wrathespecially against Mr. Calheiros.
Even as he faces a loss of authority, Mr. Calheiros, from Alagoas State in Brazil’s northeast, is expected to keep his seat in the Senate. For many of the protesters on the streets of Brazilian cities, Mr. Calheiros came to symbolize impunity in the nation’s political system, resurrecting his career despite facing an array of scandals. (In 2007, he was forced to resign as head of the Senate over the same child support case.)
It was not immediately clear if the Supreme Court would need to ratify or reject Mr. Mello’s ruling with a full vote of its members. The request for Mr. Calheiros’s ouster came from Sustainability Network, a political party in the opposition. Mr. Calheiros may be able to appeal the decision.
“I applaud this ruling,” said Randolfe Rodrigues, a senator from Sustainability Network, which largely blends centrist and leftist ideas. He said that the decision built on previous votes by justices aiming at preventing politicians on trial in corruption cases from remaining in the presidential line of succession.
Jorge Viana, a senator from Ms. Rousseff’s leftist Workers’ Party, is expected to ascend to the post as head of the Senate. Mr. Calheiros is a member of the Brazilian Democratic Movement Party, the same scandal-ridden centrist grouping led by President Michel Temer.
Senators from the Workers’ Party said on Monday night that they would seek to delay voting in the Senate on a bill that would place a cap on federal spending, a cornerstone of Mr. Temer’s proposed austerity measures. The Senate already approved the bill in a first round of voting in November, with a second and final round scheduled for mid-December.
With some in Congress now also calling for Mr. Temer’s impeachment after a scandal involving his support for an ally in a property deal, Brazil’s political establishment is facing the prospect of renewed instability. But at least for now, few observers see Mr. Temer at imminent risk of falling, given his coalition’s control of Congress.