Factbox: Brazil's presidential impeachment process

BRASILIA (Reuters) - The lower house of Brazil’s Congress opened a three-day debate on Friday on whether to impeach President Dilma Rousseff on charges of manipulating budget accounts, after the government lost a last-ditch appeal before the Supreme Court to halt the process.

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. REUTERS/Ueslei Marcelino

Here are the next steps in the presidential impeachment under Brazil’s Constitution:

1) The lower house debate is set to culminate with a vote by the full house on Sunday. A televised ballot is due to start at 2 p.m. (1700 GMT).

Rousseff’s opponents need the votes of two-thirds of 513 members of Congress, or 342. Speaker Eduardo Cunha, a fierce critic of Rousseff, does not vote.

Rousseff requires 171 votes or abstentions to block impeachment.

2) If Rousseff loses the lower house vote, the Senate must then vote on whether to go ahead with putting her on trial. The timing of this vote is unclear, but it is broadly expected to take place in early May.

Senate Speaker Renan Calheiros - a supporter of Rousseff - says the Supreme Court must provide a calendar for how the process should unfold.

A committee must be created to study the legal admissibility of the impeachment request, but not the merits of the case against Rousseff. It will then make a non-binding recommendation to the Senate.

If the Senate votes by a simple majority to accept the case, Rousseff will formally have been impeached and immediately be suspended from office. Vice President Michel Temer becomes acting president.

Senior senators have said that if the lower house sends Rousseff for trial she lacks the support in the Senate to prevent impeachment.

The Senate has 180 days to conduct its trial, chaired by the Chief Justice of the Supreme Court, Ricardo Lewandowski. Analysts say impeachment, if it goes ahead, will be a quick process given Brazil’s political crisis and could be decided by the end of May.

3) If two-thirds of the 81-seat Senate, or 54 senators, vote against Rousseff during her impeachment she is found guilty. She is then stripped of her political rights and cannot run for elected office for eight years.

Temer will be confirmed as president for the rest of Rousseff’s term, ending on Dec. 31, 2018.

It would be the first time a Brazilian president has been impeached since Fernando Collor de Mello was stripped of office in 1992 on corruption charges. He is currently a senator.

Reporting by Anthony Boadle; Editing by Daniel Flynn and Tom Brown