correction

An earlier version of this article incorrectly stated that William H. Rehnquist had not attended an Ivy League school. This version has been updated.

Former vice president Joe Biden has repeatedly promised to appoint a black woman to the Supreme Court if elected. The dearth of potential candidates in traditional pipelines, however, makes it hard to predict just who might be on any short list.

Presidents of both parties have tended to appoint justices from the same type of backgrounds in recent decades. All nine of the court’s current justices served either on a federal appellate court or as the nation’s solicitor general immediately prior to their appointment. Indeed, with one exception, every justice confirmed since 1971 has served in one of these two roles immediately prior to their appointment.

Biden likely would not follow that pattern, however, if a vacancy opened up early in his tenure. That’s because there are only three black women appointed by a Democratic president serving as active federal appellate judges. Two are 68 years old, while the third is 80. While there are no formal age limits for a first appointment, presidents have tended to appoint much younger people to the bench so that their selections would likely sit for three or even four decades before stepping down. This means Biden will have to look outside of the normal channels to keep his promise.

That’s what President Ronald Reagan did for his first court appointment. He had promised to appoint a woman to the bench if elected, and he, too, found few, if any, candidates available through traditional channels when a vacancy arose in the summer of 1981. He had to turn to an unknown judge on the Arizona state court of appeals, Sandra Day O’Connor, to keep his promise. So we should perhaps expect Biden to look at women sitting on federal district or state supreme courts were he to face a first-year vacancy.

A list of potential nominees published by the progressive advocacy group Demand Justice provides some clues as to who might be on a Biden short list. A few people stand out as potentially strong nominees.

Leondra Kruger might be at the top of that list. She has been a member of the California state Supreme Court since 2015 and previously served in the Obama administration as the principal deputy to the solicitor general. She received her bachelor’s degree from Harvard and her law degree from Yale Law School, where she was editor in chief for the Yale Law Journal, and she subsequently clerked for Justice John Paul Stevens. That’s an impeccable record of academic excellence that has typically been a strong predictor of subsequent consideration for nomination to the court. She is also only 43 years old and can be expected to serve for decades as a bulwark of the court’s progressive faction. Conservatives will surely object to her jurisprudence, but her educational record and list of accomplishments is clearly top rank.

Federal District Court Judge Ketanji Brown Jackson is another young potential nominee. Only 49 years old, Jackson also graduated from Harvard Law School and clerked for Justice Stephen G. Breyer. President Barack Obama appointed her to the U.S. Sentencing Commission in 2009, and he also interviewed her for the Supreme Court vacancy caused by Justice Antonin Scalia’s unexpected death in 2016. Jackson would be another candidate who ticks all the progressive boxes.

Anita Earls is another potential candidate. She is a 60-year-old associate justice on the North Carolina Supreme Court and served as deputy assistant attorney general in the Justice Department’s civil rights division during the Clinton administration. A graduate of Williams College and Yale Law School, Earls also has taught at several law schools and founded the Southern Coalition for Social Justice in 2007. She lacks Kruger’s and Jackson’s academic star power and youth, but she brings a long record of practical legal and activist experience that they lack.

Biden might also look beyond the courts for a nominee — for example, to Sen. Kamala D. Harris (D-Calif.). While no sitting elected official has been appointed to the Supreme Court since Dwight D. Eisenhower tapped Earl Warren, then governor of California, to become chief justice in 1953, it was once not uncommon for presidents to appoint politicians to the high court. Presidents William Howard Taft, Warren G. Harding, Herbert Hoover, Franklin D. Roosevelt and Harry S.Truman each appointed senators and governors; Taft himself joined the court after his presidency. Harris’s appointment would be a consolation prize were she not selected as Biden’s vice president, and, at 55, she’s young enough to serve a long time.

There are surely others who could qualify. What’s clear, however, is that even though Biden might have to search outside normal channels to find credible progressive black women that in itself could be a good thing. Some of the most influential justices did not have all the typical experiences of their peers, such as serving as federal judges (William H. Rehnquist) or graduating from Ivy League schools (Warren). If Biden’s promise to achieve racial and gender diversity leads to greater diversity in experiences, too, that would be good for the court’s long-term future.

Read more: