Brazil's lower house of congress is scheduled to vote on whether to allow the impeachment of President Dilma Rousseff.
Lawmakers are due to vote on Sunday on the embattled president’s fate. The pro-impeachment camp needs 342 votes, or two-thirds of the 513 votes in the chamber, to send the proceedings to the senate for a possible trial expected in May.
If the senate finds her guilty, President Rousseff would be forced to leave office. The vice president-turned-opponent, Michel Temer, would serve Rousseff’s term until 2018 if she is voted out of office.
A large number of security forces are due to be stationed on Sunday in the capital, Brasilia, and in the cities of Sao Paulo and Rio de Janeiro, where hundreds of thousands of pro- and anti-impeachment people are expected to hit the streets.
A two-meter-high wall stretching for more than one kilometer (0.6 mile) has been built outside the congress in Brasilia to keep the opposing camps apart.
Recent polls show that over 60 percent of Brazil's 200 million people back impeaching Rousseff.
The president fought for survival on Saturday, lobbying some wavering congressional deputies behind closed doors on the eve of the vote.
Rousseff’s government stands accused of violating fiscal rules to promote her 2014 re-election campaign.
The president is also under fire over a graft scandal at the state oil company, Petrobras, where she was the manager before taking office as president in 2010.
Recently, she further angered the opposition by giving her predecessor and ally, Luiz Inacio Lula da Silva, who is himself implicated in the corruption case, a top position in the cabinet. Opponents say the move is aimed at granting him immunity from prosecution.
However, Rousseff has denied the allegations against her as politically-motivated, vowing not to back down.