CNN  — 

Supreme Court Justice Stephen Breyer plans to retire, setting up a seismic confirmation battle at the start of a midterm election year as President Joe Biden tries to find his footing with his agenda stalled and Democrats divided in Congress.

Breyer, 83, is expected to stay on until the end of the court term and until a replacement is confirmed, a well-placed source familiar with the matter told CNN.

He informed Biden of his plans last week and will formally announce his retirement at a White House event with the President as early as Thursday, two sources told CNN.

Although Biden’s pick will not change the balance of the court, given that Breyer will almost certainly be replaced with a fellow liberal, the new nominee is expected to be much younger and could serve on the court for decades. The court currently has six conservative justices appointed by Republican presidents, and three liberals appointed by Democrats.

On the campaign trail, Biden vowed that if he were to get a vacancy he would fill it with an African American woman, which would represent a historic first for the high court. White House press secretary Jen Psaki told reporters Wednesday that Biden “certainly stands by” the promise, but declined to offer any specifics.

Potential candidates include Judge Ketanji Brown Jackson, 51, who was confirmed last year to the powerful DC-based appellate court. She once served as a law clerk for Breyer, and also worked as an assistant federal public defender and served on the US Sentencing Commission.

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Another possibility would be Justice Leondra Kruger, 45, who serves on the California Supreme Court and is a veteran of the US Solicitor General’s office. Members of Biden’s team have previously stressed that they are seeking diversity for judicial appointments and that they are prepared to break from the norm and consider those whose legal experiences have been historically underrepresented on the federal bench, including those who are public defenders and civil rights and legal aid attorneys.

The timing of Breyer’s decision to retire comes as he has faced an intense pressure campaign from the left, which urged him to leave the court while Biden has a clear path to replace him.

Democrats have been burned repeatedly by timing, Republican gridlock and the refusal of another justice to retire when the political circumstances were ripe.

Notably, Justice Ruth Bader Ginsburg did not heed calls that she retire at the beginning of former President Barack Obama’s second term, when Democrats still controlled the Senate. Her death weeks before the 2020 election allowed then-President Donald Trump to make the pivotal appointment of Justice Amy Coney Barrett to the bench, which moved the court further to the right.

Meanwhile, the confirmation fight to fill the vacancy left open by Justice Antonin Scalia’s unexpected February 2016 death showed Republicans’ willingness to block appointments by Democratic presidents. The Senate, then controlled by the GOP, refused to consider Obama’s nominee for the seat, Merrick Garland, and Trump then filled it with Justice Neil Gorsuch, with Senate Republicans lowering the threshold vote from a 60-vote requirement to a bare majority to do so. The maneuver deprived Democrats of what was likely a once-in-a-generation opportunity to flip the court’s balance.

Senate Majority Leader Chuck Schumer said Biden’s nominee “will receive a prompt hearing in the Senate Judiciary Committee, and will be considered and confirmed by the full United States Senate with all deliberate speed.”

In the current 50-50 Senate, all Democrats would need to stay united with Vice President Kamala Harris breaking a potential tie in the event no Republicans break ranks. But Senate Democrats are confident that Biden’s nominee, whomever he selects to replace Breyer, will receive enough votes to for confirmation, according to senior Democratic sources.

Asked if Republicans intend to block the President’s nominee, Senate GOP Leader Mitch McConnell told reporters Wednesday, “We don’t even know who the nominee is yet,” adding that he’ll have more to say on Breyer’s “long and distinguished career” after his official retirement announcement.

South Carolina Republican Sen. Lindsey Graham, who voted for Obama’s first two nominees, said the GOP won’t be able to block Biden’s choice.

“If all Democrats hang together – which I expect they will – they have the power to replace Justice Breyer in 2022 without one Republican vote in support,” Graham said in a statement. “Elections have consequences, and that is most evident when it comes to fulfilling vacancies on the Supreme Court.”

Biden on Wednesday afternoon declined to weigh in on the retirement news.

“Every justice has the right to decide what he or she is going to do, and announce that on their own,” Biden told reporters in the State Dining Room. “There’s been no announcement from Justice Breyer – let him make whatever statement he is going to make, and I’ll be happy to talk about it later.”

Breyer, a consistent liberal vote on the Supreme Court with an unflappable belief in the US system of government and a pragmatic view of the law, has served nearly three decades on the bench.

Appointed in 1994 by then-President Bill Clinton, Breyer has sought to focus the law on how it could work for the average citizen. He was no firebrand and was quick to say that the Supreme Court couldn’t solve all of society’s problems. He often stressed that the court shouldn’t be seen as part of the political branches but recognized that certain opinions could be unpopular.

“It is wrong to think of the court as another political institution,” Breyer told an audience at Harvard Law School in 2021. “It is doubly wrong to think of its members as junior league politicians.”

“If the public sees judges as ‘politicians in robes,’” he warned, “its confidence in the courts, and in the rule of law itself, can only diminish, diminishing the court’s power, including its power to act as a ‘check’ on the other branches.”

The news comes as the court’s conservative majority has flexed its muscles in a blockbuster term. The justices have already heard one case that could overturn Roe v. Wade and another that could expand gun rights. Recently, Breyer joined his liberal colleagues, Justice Sonia Sotomayor and Elena Kagan, in a bitter dissent when the conservative majority blocked Biden’s vaccine mandate for large employers. Breyer also dissented last year when the court allowed a Texas six-week abortion ban to remain in effect. The law is the strictest in the nation and bars abortion before most women even know they are pregnant.