Those competing visions mirror the increasingly polarized election campaign in which a hard-right former army officer, Jair Bolsonaro, is now second in the polls behind Lula, with centrists struggling to make ground.
On the eve of the session, the country's army commander raised eyebrows - and was widely celebrated and condemned online - with tweets subtly supporting da Silva's incarceration.
Despite the conviction and several other corruption charges against him, Mr da Silva leads all preference polls for the election.
Da Silva was convicted previous year of helping a construction company get sweetheart contracts in exchange for the promise of a beachfront apartment.
6 out of 11 judges late on Wednesday rejected a request from the leftist political leader to stay free from conviction in a vote that is likely to end his political career and set to further divide Brazil before national elections in October.
However, in January, an appeals court unanimously increased the sentence to 12 years, the report said.
The Brazilian Democratic Movement party will formally decide which candidate it hopes to move forward with a selection to lead its party in the national election in either the month of June or July, during the Brazilian winter. After the ruling, Lula's Workers' Party said it was a "tragic day for democracy in Brazil".
Wednesday's nationally televised session at the Supreme Federal Tribunal comes a time of high tension in Latin America's largest nation.
Last year, Temer was twice charged with corruption but remained in office because in both cases Congress, which must vote on criminal cases involving a sitting president, made a decision to spare him prosecution.
Lula, 72, was convicted by regional Judge Sergio Moro for passive corruption and money laundering, and his 10-year prison sentence was actually lengthened to more than 12 years during the appeal process.
Supporters hail Moro as a hero taking on endemic corruption while detractors, particularly supporters of da Silva's Workers' Party, consider him a partisan hit man. The Superior Electoral Court could decide to make such an exception if Lula registers as a presidential candidate before the August 15 deadline.
On the right, Lula is considered the face of corruption sweeping the country's political elite.
His conviction stemmed from a wide-ranging corruption investigation into the state-run oil company Petrobras, dubbed Operation Car Wash.
However, in an unrelated case in 2016, the Supreme Federal Tribunal disagreed with that logic, ruling that a convict could start serving a sentence after a first appeal was denied.