Rio de Janeiro (CNN) Brazilian President Dilma Rousseff is fighting for survival -- and it looks increasingly likely she won't make it.

On Sunday, weeks of raucous debates inside Congress and rival protests outside will come to a head when the lower house votes whether to impeach the President.

If the motion is approved, Rousseff could be suspended as early as May. That would be about three months before the Summer Olympics kick off in Rio, an event that was supposed to showcase Brazil as a rising power on the global stage.

Two-thirds of the 513 lawmakers would need to approve the impeachment motion for it to continue to the Senate.

Photos: Mass anti-government protests in Brazil Police use water cannons Friday, March 18, to clear the main avenue of Sao Paulo, Brazil, where people were protesting Brazilian President Dilma Rousseff and her ministerial appointment of former President Luiz Inacio Lula da Silva. Rousseff named Lula da Silva as her chief of staff, and her critics say it is an attempt to shield him from a corruption investigation. Hide Caption 1 of 20 Photos: Mass anti-government protests in Brazil Police use water cannons on Sao Paulo protesters on March 18. Many Brazilians are also frustrated with a spiraling economy. Hide Caption 2 of 20 Photos: Mass anti-government protests in Brazil Demonstrators gather next to the presidential palace in Brasilia on Thursday, March 17. Hide Caption 3 of 20 Photos: Mass anti-government protests in Brazil Protesters face off with police in Brasilia on March 17. Hide Caption 4 of 20 Photos: Mass anti-government protests in Brazil A demonstrator clasps his hands during protests in Sao Paulo on March 17. Hide Caption 5 of 20 Photos: Mass anti-government protests in Brazil Demonstrators call for Rousseff's resignation outside the presidential palace in Brasilia on Wednesday, March 16. Hide Caption 6 of 20 Photos: Mass anti-government protests in Brazil A woman waves a Brazilian national flag in front of a line of riot policemen in Brasilia on March 16. Hide Caption 7 of 20 Photos: Mass anti-government protests in Brazil Demonstrators protest in Sao Paulo on March 16. Hide Caption 8 of 20 Photos: Mass anti-government protests in Brazil An impeachment sign is carried in Sao Paulo on March 16. Hide Caption 9 of 20 Photos: Mass anti-government protests in Brazil Riot police stand guard outside the presidential palace in Brasilia on March 16. Hide Caption 10 of 20 Photos: Mass anti-government protests in Brazil Demonstrators in Sao Paul carry a balloon depicting Lula da Silva as a convict on March 16. Hide Caption 11 of 20 Photos: Mass anti-government protests in Brazil Demonstrators throw tear gas back at riot police during a protest in Brasilia on March 16. Hide Caption 12 of 20 Photos: Mass anti-government protests in Brazil Demonstrators protest in Brasilia on March 16. Hide Caption 13 of 20 Photos: Mass anti-government protests in Brazil Demonstrators protest in front of the presidential palace on March 16. Hide Caption 14 of 20 Photos: Mass anti-government protests in Brazil A police officer uses pepper spray on protesters to keep them from getting closer to the Congress building in Brasilia on March 16. Hide Caption 15 of 20 Photos: Mass anti-government protests in Brazil Soldiers in riot gear block the presidential palace on March 16. Hide Caption 16 of 20 Photos: Mass anti-government protests in Brazil A demonstrator is dressed as Lula Da Silva during a protest in Rio de Janeiro on Sunday, March 13. Hide Caption 17 of 20 Photos: Mass anti-government protests in Brazil A painted man in Manaus, Brazil, holds a placard supporting Congressman Jair Bolsonaro for President on March 13. Hide Caption 18 of 20 Photos: Mass anti-government protests in Brazil Thousands of demonstrators protest in Manaus on March 13. Hide Caption 19 of 20 Photos: Mass anti-government protests in Brazil A demonstrator protests in Manaus on March 13. Hide Caption 20 of 20

"Not only is the impeachment vote in the plenary of the lower house of Congress this Sunday looking increasingly likely, but it will most likely prevail by a wide margin," according to analyst Christopher Garman of Eurasia Group.

According to polls in the country's three major newspapers, the opposition has already secured the 342 votes it needs. Rousseff is accused of breaking budget laws to mask a deficit ahead of her re-election in 2014.

Rousseff was due to address the nation in a pretaped message Friday evening but canceled, according to a presidential source. No reason was given. Rousseff was expected to appeal to public opinion in an effort to prevent her impeachment.

She has repeatedly denied committing any crime and calls the impending impeachment trial a "coup d'etat" aimed at removing a democratically elected leader by any means possible.

This comes after the Supreme Court denied a last-minute motion filed by the attorney general requesting the impeachment trial be blocked.

Police have erected a 1 kilometer long barricade on the lawn in front of Congress to separate anti-government protesters from Rousseff supporters. Huge crowds have already started to converge on the capital of Brasilia.

Opponents blame Rousseff for the worst recession in decades, now in its second year. They also hold her accountable for a massive bribery and corruption scandal that has engulfed dozens of politicians in her Workers Party and coalition government.

Although Rousseff has not been implicated in the scandal, for many years she was the chairwoman of the state-run oil company Petrobras, which is at the heart of the investigation.

Her supporters argue that the impeachment trial is a petty revenge orchestrated by politicians accused of much more serious crimes, led by Eduardo Cunha, the leader of the lower house of Congress.

Cunha has been accused of corruption and holding secret Swiss bank accounts.

His PMDB party, the largest in Brazil, abandoned the governing coalition last month, leaving Rousseff increasingly isolated as the impeachment proceedings unfolded.

They ordered all six of their ministers to step down from Rousseff's Cabinet. Vice President Michel Temer, also of the PMDB and the next in line for the presidency, kept his post.

Rousseff's exit would mark the end of an era for the Workers Party, which assumed the presidential office in 2004 with the election of former President Luiz Inacio Lula da Silva

During Lula da Silva's two terms, the left-leaning party was credited with lifting millions of Brazilians out of extreme poverty through increased social spending, largely financed by booming commodities exports to China.

But under Rousseff, his hand-picked successor, those exports dried up. The economy started to drop at the same time the corruption investigation revealed a history of bribes involving the country's biggest construction companies, Petrobras and dozens of politicians.

Last month, Lula da Silva was taken in for questioning on suspicion he benefited from the scheme during his tenure and afterward.

A few days later, Rousseff sought to appoint her former mentor as her chief of staff , which would have given him certain protections from prosecution. The move fueled nationwide protests.

The problem is that there is no quick fix going forward.

If the impeachment trial goes to the Senate and is approved there, Rousseff would have to step down for 180 days to defend herself against accusations.

She would be replaced by Temer, whose party, the PMDB, has also been implicated in the corruption scheme and could be further weakened by the ongoing investigation.

Rousseff's supporters have vowed to take to the streets in retaliation, ensuring a long battle ahead.