Brazilian president's trial underway but impeachment is 'a done deal'

Nine months since impeachment proceedings began for Brazilian President Dilma Rousseff, the last stage of the process is finally underway.

The country's senate began a trial on Thursday, which is expected to last until next week. Rousseff herself will appear in-person on Monday and senators will then take a final vote, either on August 30 or 31, on whether she should be impeached.

The trial is set to confirm what Brazil-watchers have long anticipated: the country's first female head of state will be forced from office, and current Vice President Michel Temer will take her place.

Of the 81 senators, 54, or two-thirds, must vote for impeachment for Rousseff's ouster to happen, and strategists say that's already a done deal.

"We've last strong indications that over two-thirds of senators are likely to vote for impeachment," Monica de Bolle, non-resident senior fellow at the Peterson Institute for International Economics (PIIE), told CNBC's "Squawk Box." "So, we could have a new official Temer government by September 6 or 7."

Likewise, political consultancy Eurasia said there was a 90 percent probability the impeachment vote would pass, according to a Friday note.

No changes to Congress are expected once Temer takes over; his team and cabinet will remain in place until the country's next general elections in 2018.

A frenzied trial

Despite the consensus on the outcome, the trial is still expected to be ugly.

Senators Ronaldo Caiado (R) and Lindbergh Farias (back) exchange insults during the Senate impeachment trial of Brazilian suspended President Dilma Rousseff at the National Congress in Brasilia on August 25, 2016.
EVARISTO SA | AFP | Getty Images

There were heated arguments between senators on Thursday, with insults such as "scoundrel" tossed around, according to media reports. Rousseff still has a number of senators faithful to her, including Gleisi Hoffman who reportedly told peers that none of them had the moral authority to judge the president.

The bickering ultimately forced Chief Justice Ricardo Lewandowski to briefly suspend the session to restore order.

"Impeachment is a traumatic process," explained de Bolle. "The country is still split. There are those who view this entire process as something that was manipulated by Temer and his Brazilian Democratic Movement party (PMDB)."

The PMDB, once a staunch ally of Rousseff's ruling Working Party, is now the latter's main opposition.

Rousseff is accused of breaking budget laws. Her critics say she spent state funds without congressional approval and falsified accounts to hide Brazil's widening deficit while campaigning for re-election in 2014. Rousseff denies the charges, and more arguments are anticipated on Monday when the 68-year old presents her defense to senators.

"While her presence may have an effect on public opinion, it won't be enough to tip the balance in her favor in the senate," Eurasia predicted. Rousseff has called the impeachment a coup, but if she maintains that strategy on Monday, it's unlikely to resonate well with moderates, the consultancy explained.

"This [her appearance on Monday] would not change the outcome of the impeachment trial, but it might help the Worker's Party in municipal elections later this year," Andrea Murta, deputy director of the Adrienne Arsht Latin America Center, a Washington-based think-tank, told CNBC.

Last-minute surprises?

Murta did flag a point that may impact the outcome of the final vote next week.

It remained to be seen whether the parties that were currently forming the interim government coalition would vote as a block or if they would have significant defections, she said. "Rumor has it that part of the PMDB might break away from the Michel Temer government."

There was also speculation that Rousseff may resign before the vote.

"That's unlikely to happen given her history and the tone of her defense in recent months," Eurasia said. "More importantly, a resignation would not change the ultimate outcome [i.e. of Temer assuming office]."

"Rumors had it that the senate could acquit Rousseff should she resign, arguably restoring her political rights, but this deal seems far-fetched and too convoluted to be executed."

—Follow CNBC International on Twitter and Facebook.