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.