Brazilian President Dilma Rousseff went on the offensive Saturday, a day ahead of a scheduled vote on her impeachment, labeling opponents as corrupt.

The leftist leader could be toppled by Congress. The impeachment debate began Friday, and a vote in the House to send the case to the Senate for trial is expected late Sunday.

“This is a historic process, there's no doubt,” House Speaker Eduardo Cunha, one of the leaders of the ouster movement, said during a raucous session Friday. Cunha himself is accused of taking millions of dollars in the embezzlement scheme at the heart of the Petrobras scandal, which involved companies allegedly bribing senior Petrobas officials to overbill contracts, allowing for the skimming of the excess funds and payment of kickbacks. Rousseff is not being investigated as a participant in the embezzlement, but she was the company’s chairwoman as the alleged scheme was hatched. 

impeachment Lower House members who support the impeachment demonstrate during a session to review the request for Brazilian President Dilma Rousseff's impeachment, at the Chamber of Deputies in Brasilia, Brazil, April 15, 2016. Photo: Ueslei Marcelino/Reuters

Rousseff, 68, was set to leave her office at the Palacio do Planalto and address an expected 100,000 supporters Saturday at the Mane Garrincha stadium.

“We came to join the defense of democracy and the government that was legitimately elected in 2014,” Tiago Almeida, 35, a metal worker from the state of São Paulo, told Agence France-Presse.

In an op-ed piece published in Folha de São Paulo, Rousseff accused those opposing her of corruption.

“They want to convict an innocent woman and save the corrupt. ... Would those leading the coup allow the fight against corruption to continue? What's their legitimacy?” she asked.

Rousseff, who accuses her accusers of attempting to stage a coup, is facing allegations of covering up the size of the budget deficit during her 2014 re-election campaign. She has defended her actions, saying they are similar to what her predecessors had done.

Brazilian newspapers say ouster leaders have the votes necessary to send the case to the Senate, which then would need to vote on whether to accept the case, the BBC said. If the Senate accepts the case, Rousseff will be suspended from office for six months while the case is tried, putting Vice President Michel Temer in charge.

The Organization of American States has concluded the impeachment process is flawed.

“There is no criminal accusation against the president. Rather, she has been accused of the poor administration of public resources in 2014,” said OAS leader Luis Almagro, who is visiting Brazil. “This is an accusation that is political in character and that does not merit an impeachment process.”