Constitutional law professor and attorney Lênio Streck said Mr. Barroso’s retirement opens the way for President Lula to nominate someone who could remain on the court for roughly two decades. “One key factor is appointing someone younger, and that’s exactly what Lula will do—I have no doubt. The president will choose a highly aligned, organic candidate,” Mr. Streck said, pointing to Mr. Messias as the favorite.

According to Mr. Streck, naming either Mr. Pacheco or Mr. Dantas would steer the choice toward a more political discussion, something the government is likely to avoid.

For Roberto Dias, a professor of law at FGV Direito SP, the ideal profile to replace Mr. Barroso would resemble that of current Chief Justice Edson Fachin: “A justice who speaks primarily through court opinions, avoids political circles, and reinforces the perception of impartiality at the Supreme Court, especially at a time when the court continues to face fierce criticism.”

Mr. Dias noted that while the leading contenders meet constitutional requirements of “impeccable reputation and distinguished legal expertise,” they are closely tied to politics. He argued that Mr. Lula should instead consider appointing a woman, preferably a Black woman, to promote greater representation on the court.

“In the Supreme Court’s composition, people with diverse perspectives are essential to forming more consistent decisions that reflect the diversity and pluralism enshrined in the Federal Constitution,” he said.

Criminal law expert and PUC-SP professor Conrado Gontijo agreed that Mr. Messias, Mr. Pacheco, and Mr. Dantas possess undeniable legal credentials, having held important positions throughout their careers.

Mr. Gontijo said Mr. Barroso played a central role in key democratic debates during his tenure at the Supreme Court, fulfilling with “absolute rigor” the constitutional mission entrusted to the court’s justices. During Mr. Barroso’s tenure as chief justice, he added, the court faced enormous and unprecedented challenges, including “serious and unfounded attacks.” “His unwavering defense of the Constitution and all it represents was vital to preserving Brazil’s institutional framework,” Mr. Gontijo said.

Attorney Antônio Carlos de Almeida Castro, known as Kakay, praised Mr. Barroso’s performance as both justice and president of the Supreme Court, as well as his leadership of the Superior Electoral Court (TSE). “The open confrontation initiated by [then-President] Bolsonaro, who insulted and vilified him, shows that Barroso was on the right side and that he clearly unsettled the far-right faction in power at the time,” Mr. Castro said.

Mr. Streck divided Mr. Barroso’s Supreme Court stint into two distinct phases. In the first, the justice supported Car Wash Operation, the now questioned anti-corruption task force, adopting a more “punitive” stance. In the second, particularly over the past two years, during his presidency, Mr. Barroso became a key defender of democracy as the Supreme Court came under attack from the Bolsonarist movement.

Throughout his tenure, Mr. Streck emphasized, Mr. Barroso consistently acted in defense of the Constitution and individual rights. He cast votes advancing social rights for minorities, Indigenous peoples, racial quotas, and same-sex marriage, even while maintaining a more liberal stance on labor reform.