RIO DE JANEIRO — A crucial part of Brazil’s governing coalition withdrew support for President Dilma Rousseff on Tuesday, a move that could increase the likelihood of her impeachment and deepen Brazil’s political and economic crises.
The leadership of the Brazilian Democratic Movement Party, or the PMDB, which has 68 members in the lower house of Congress, the most of any party, voted to split with Ms. Rousseff’s Workers’ Party. That lays the groundwork for more of its members to vote to impeach Ms. Rousseff. That will most likely happen next month.
Several of Ms. Rousseff’s ministers, who belong to the PMDB, were asked by their party leaders to step down. They included the health minister, Marcelo Castro, who had been leading the country’s efforts to address the Zika virus outbreak, and the civil aviation minister. The request comes just months before the start of the Summer Olympics in Rio de Janeiro.
Increased government paralysis is seen as one consequence.
After the PMDB decision, Ms. Rousseff canceled a trip to Washington, where she was supposed to participate in a nuclear security summit meeting this week.
In Brasília, Romero Jucá, a senator who led Tuesday’s meeting, which lasted less than five minutes, said, “Nobody in the country is authorized to serve in any federal appointment in the name of the PMDB party.”
While the PMDB includes both longtime opponents and supporters of Ms. Rousseff, she cannot afford to lose any votes in Congress.
After narrowly winning re-election in late 2014, Ms. Rousseff has struggled to show leadership as bad economic news worsened, and an unprecedented corruption scandal widened involving the state oil company, Petrobras.
While Ms. Rousseff has denied that her campaigns received any illegal money, or that she had any knowledge of corruption at Petrobras, criticism of her grew this month after she named the former president, Luiz Inácio Lula da Silva, to her cabinet. That appointment was seen in some circles as a way to shield him from arrest by prosecutors who are investigating graft accusations against him.
Subsequently, impeachment proceedings against Ms. Rousseff began in a committee in Brazil’s lower house. That committee is expected to vote in April. The full house would then vote. If it voted to impeach, and then the Senate voted to open proceedings, Ms. Rousseff would be suspended for 180 days while she went on trial. Brazil’s vice president, Michel Temer, who leads the PMDB, but did not attend Tuesday’s meeting, would then temporarily take over, with the ability to appoint ministers and enact policy.
Ms. Rousseff still has opportunities to thwart impeachment, or at least delay the proceedings. If the full lower house voted to impeach, she could appeal to the high court and the Senate would have to await a ruling before voting on whether it could commence its own impeachment deliberations.
Moreover, at any time between now and then, Ms. Rousseff also has other legal remedies. “She can appeal at any moment she finds something legally questionable occurring in the process,” said Brasílio Sallum Jr., a professor of sociology at the University of São Paulo and an expert in Brazil’s political processes.
Her legal strategy aside, many question how the removal of Ms. Rousseff, by itself, would help the country out of its predicaments.
“Impeachment alone may not be the solution to the crisis,” said João Augusto de Castro Neves, the Latin America regional director of the Eurasia Group, a political risk consulting firm.
That is largely because many other leaders, particularly in the PMDB, have been implicated in the Petrobras investigation. While Mr. Temer has not been implicated, he would be vulnerable to political fallout from problems faced by his colleagues.
It is also unclear how much public support he has. His approval ratings are not much higher than Ms. Rousseff’s.
“All of these scenarios — one in which she survives, the other one in which Temer takes over, and the new elections scenario — they all point to very tough policy making in the next year or two,” Mr. Castro Neves said.
He foresaw “governments that are relatively weak or won’t have enough political capital to do everything that needs to be done to fix the economy.”
It is unclear how much public support the PMDB will have. Following the vote on Tuesday, Marina Silva, a longtime critic of Ms. Rousseff, denounced the PMDB for its move, saying it was “equally responsible” for the country’s political and economic crisis.
The party is widely viewed as one that stands for no principles or ideology except staying in power. It does not field candidates in presidential elections but rather looks to play a decisive role in helping the winner.
It has long been an irritant to both Ms. Rousseff and her predecessor, Mr. da Silva.
State Department officials have taken note. In a 2004 cable, made available by WikiLeaks, American diplomats observed that “the PMDB has never pretended to be more than a high-maintenance ally-of-convenience whose constant sniping often exposes coalition fissures.”
Whether the PMDB leadership’s decision to abandon Ms. Rousseff will prove politically expedient remains unclear. Some prominent members have sharply criticized it.
On Tuesday, Brazil’s minister of agriculture, Kátia Abreu, a PMDB member, defended Ms. Rousseff in an interview with Globo Rural.
Ms. Abreu said that she thought what was happening to Ms. Rousseff was unmerited and that impeachment would be “traumatic” for the country.
Because of an editing error, an article on Wednesday about a party in Brazil’s governing coalition that withdrew its support from the embattled president, Dilma Rousseff, misstated the status of some of Ms. Rousseff’s cabinet ministers. Several ministers who belong to the Brazilian Democratic Movement Party have been asked by the party leadership to resign; they have not stepped down.