President Joe Biden is eyeing at least three judges for an expected vacancy on the Supreme Court as he prepares to quickly deliver on his campaign pledge to nominate the first Black woman to the nation’s highest court, according to aides and allies.

Biden and Justice Stephen Breyer are expected to hold an event at the White House Thursday to formally announce Breyer’s plans to retire, according to a person briefed on the planning who was not authorized to publicly discuss it in advance.

Early discussions about a successor are focusing on U.S. Circuit Judge Ketanji Brown Jackson, U.S. District Judge J. Michelle Childs and California Supreme Court Justice Leondra Kruger, according to four people familiar with the matter who spoke on condition of anonymity to discuss White House deliberations. Jackson and Kruger have long been seen as possible nominees.

Since Biden took office in January 2021, he has focused on nominating a diverse group of judges to the federal bench, installing five Black women on federal appeals courts, with three more nominations pending before the Senate. Other possible candidates for the high court could come from among that group, Biden aides and allies said, especially since almost all of the recent Supreme Court nominees have been federal appeals judges.

Read:Justice Breyer to retire, giving Biden first court pick

“He has a strong pool to select a candidate from, in addition to other sources. This is an historic opportunity to appoint someone with a strong record on civil and human rights,” said Derrick Johnson, the NAACP’s president.

By the end of his first year, Biden had won confirmation of 40 judges, the most since President Ronald Reagan. Of those, 80% are women and 53% are people of color, according to the White House.

Jackson, 51, was nominated by President Barack Obama to be a district court judge. Biden elevated her to the U.S. Court of Appeals for the District of Columbia Circuit. Early in her career, she was also a law clerk for Breyer.

Childs, a federal judge in South Carolina, has been nominated but not yet confirmed to serve on the same circuit court. Her name has surfaced partly because she is a favorite among some high-profile lawmakers, including Rep. James Clyburn, D-S.C.

Kruger, a graduate of Harvard and Yale’s law school, was previously a Supreme Court clerk and has argued a dozen cases before the justices as a lawyer for the federal government.

Breyer, 83, will retire at the end of the summer, according to two sources who confirmed the news to The Associated Press on Wednesday. They spoke on condition of anonymity so as not to preempt Breyer’s formal announcement.

But the Senate can confirm a successor before there is a formal vacancy, so the White House was getting to work and it was expected to take at least a few weeks before a nomination was formalized.

Biden said Wednesday he wasn’t going to get ahead of Breyer’s announcement.

“Every justice should have an opportunity to decide what he or she is going to do and announce it on their own,” Biden said. “Let him make whatever statement he’s going to make and I’ll be happy to talk about it later.”

When Biden was running for the White House, he said that if he had the chance to nominate someone to the court, he would make history by choosing a Black woman. And he’s reiterated that pledge since.

“As president, I’d be honored, honored to appoint the first African American woman. Because it should look like the country. It’s long past time,” Biden said in February 2020 shortly before South Carolina’s presidential primary.

Adding a Black woman to the court would mean a series of firsts — four female justices and two Black justices serving at the same time on the nine-member court. Justice Clarence Thomas is the court’s only Black justice and just the second ever, after Thurgood Marshall.

And Biden would have the chance to show Black voters increasingly frustrated with a president they helped to elect that he is serious about their concerns, particularly after he has been unable to push through voting rights legislation.

At the same time, Breyer’s replacement by another liberal justice would not change the ideological makeup of the court. Conservatives outnumber liberals by 6-3, and Donald Trump’s three nominees made an already conservative court even more conservative.

Senate Majority Leader Chuck Schumer, D-N.Y., 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.”

But Republicans in particular remain upset about Justice Brett Kavanaugh’s contentious 2018 hearing. Still, Democrats have the 50 votes plus a tiebreaker in Vice President Kamala Harris that they need to confirm a nominee.

Read: Supreme Court halts Biden’s COVID-19 vaccine rule for US businesses

Republicans who changed the Senate rules during the Trump-era to allow simple majority confirmation of Supreme Court nominees appeared resigned to the outcome. Sen. Lindsey Graham of South Carolina, an influential Republican on the Senate Judiciary Committee, said in a statement, “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.”

Nonetheless, Democrats have also been unable to get all their members on board for Biden’s social and environmental spending agenda or to move forward with a voting rights bill.

As a senator, Biden served as chairman of the Judiciary Committee, overseeing six Supreme Court confirmation hearings from 1987 to 1995, including Breyer’s.

And one person who will be central to Biden’s process is chief of staff Ron Klain, a former Supreme Court law clerk and chief counsel to that committee.

Two other Black women whom Biden appointed to federal appeals courts are also seen as contenders: Holly Thomas, a longtime civil rights lawyer he named to the U.S. Court of Appeals for the 9th Circuit, and Candace Jackson-Akiwumi, a former public defender he named to the U.S. Court of Appeals for the 7th Circuit.

Biden could also choose someone from outside the judiciary, though that seems less likely. One contender would be the head of the NAACP Legal Defense and Educational Fund, Sherrilyn Ifill, 59. She has headed the fund since 2013 and has announced she is stepping down in the spring.

The Supreme Court has had three women on it for more than a decade, since 2010, when Obama named Justice Elena Kagan to the court to replace the retiring John Paul Stevens. Kagan joined Obama’s other nominee, Justice Sonia Sotomayor, the court’s first Latina justice, and Justice Ruth Bader Ginsburg. When Ginsburg died in September 2020, Trump announced his choice of Amy Coney Barrett eight days later.