By Anthony Boadle

BRASILIA (Reuters) - Brazil's Senate started the trial of suspended President Dilma Rousseff on Thursday after a lengthy impeachment process that has paralyzed the politics of Latin America`s largest nation and is expected to culminate in her removal from office next week.

Supreme Court Chief Justice Ricardo Lewandowski reminded Senators that they must act as judges and put aside their political views.

Thursday's session will hear witnesses for and against Rousseff, Brazil's first female president, who is charged with breaking budget laws.

The leftist leader, whose popularity has been hammered by a deep recession and massive corruption scandal since she won reelection in 2014, will appear before the 81 senators on Monday to defend herself, but her opponents are confident they have more than the 54 votes needed to convict her.

Authorities prepared barriers to contain demonstrations outside Brazil's modernistic Congress building, but few Rousseff supporters have turned out, pointing to the isolation of the impeached president.

"Every one of you should vote as an individual and not according to party," Lewandowski told senators in his opening remarks.

Some two hours later, however, Lewandowski had to suspend the session briefly when a verbal fight broke out between senators.

If the final vote, which is expected late Tuesday or in the early hours of Wednesday, goes against Rousseff it would confirm her vice president, Michel Temer, as Brazil's new leader for the rest of her four-year term through 2018, ending 13 years of left-wing Workers Party rule.

A survey published by O Globo newspaper on Thursday showed that 52 senators were committed to voting to dismiss Rousseff, with only 19 supporting her and 10 undecided or not polled.

Rousseff, a former leftist guerrilla, is charged with spending without Congressional approval and manipulating government accounts to mask the extent of the deficit in the run-up to her 2014 re-election.

Temer's right-leaning government held last-minute talks with senators and political parties to shore up votes against Rousseff, who has denied any wrongdoing and described efforts to oust her as a "coup." She has refused to resign and said such accounting practices were also commonly used by previous governments.

However, the trial has become a test of support for Rousseff amid the deepest recession since the Great Depression and a massive kickback scandal surrounding state-led oil company Petrobras that has implicated dozens of politicians from her coalition, including Temer's own party.

DAUNTING TASK

If he is confirmed as president by Rousseff's ouster, Temer would face a daunting task: steering Latin America's largest economy out of recession and plugging a budget deficit that topped 10 percent of gross domestic product.

In the unlikely case that she is acquitted, Rousseff would immediately return to office.

Brazilian assets have rallied on prospects of a more market-friendly government, with the currency rising around 30 percent against the dollar this year. Still, investors and members of Temer's fragile coalition are concerned he has yet to unveil measures to control the deficit.

Temer's team has sought to speed up the trial so he can set about restoring confidence in a once-booming economy and remove any doubts about his legitimacy.

A draft budget for next year is not expected in Congress until Aug. 31, after the Senate votes, by which time Temer could have more political leverage to push through austerity measures.

"Failure to deliver tangible steps toward fiscal consolidation may trigger adverse market dynamics," Alberto Ramos, chief Latin American economist at Goldman Sachs, said in a note to clients.

Investors hope to see an end to spending concessions to pressure groups, such as a pay rise for judges that Lewandowski has pushed for.

If Rousseff is removed, Temer must be sworn in by the Senate. He is then expected to address the nation before heading to the summit of the G20 group of leading economies in China on Sept. 4-5.

If she is stripped of her presidential status, Rousseff could find herself in court in an investigation into whether she and former president Luiz Inacio Lula da Silva tried to obstruct the Petrobras corruption probe.

In her last rally before the trial, Rousseff`s supporters chanted "Out with Temer" in Brasilia on Wednesday.

"I committed no crime. To stop this from happening again, I must go to the Senate to defend Brazil's democracy, the political views that I advocate and the legitimate rights of the Brazilian people," she said.

Yet even Rousseff's Workers Party, hurt by corruption scandals and her dismal economic record, has distanced itself from her last-minute call for elections to resolve the crisis.

The last time a Brazilian president was suspended from office was in 1992, when Fernando Collor de Mello was placed on trial for corruption. He resigned from office shortly before he was found guilty by the Senate.

(Editing by Jeffrey Benkoe and Alistair Bell)