Jackson, whom President Joe Biden nominated to replace Merrick Garland on the high-profile D.C. Circuit Court of Appeals when he picked Garland for attorney general, is a Harvard Law graduate who served as a clerk to Breyer from 1999-2000 and interviewed with former President Barack Obama for former Justice Antonin Scalia's vacancy in 2016.
After the Supreme Court, the D.C. Circuit Court of Appeals is the most important federal court in the country, with jurisdiction over cases involving Congress and the executive branch agencies.
Biden, who has said he would appoint the first African American woman to the Supreme Court because the court should "look like the country," would be able to make good on that promise with a Jackson nomination. No Black woman has ever been nominated to the high court.
Other top contenders include Judge Leondra Kruger, of the California Supreme Court; Judge Leslie Abrams Gardner, of the US District Court Georgia; and Judge J. Michelle Childs, of the US District Court South Carolina.
Once Biden nominates a replacement, Senate Democrats plan to not only hold a confirmation hearing swiftly -- Justice Amy Coney Barrett had her first hearing 13 days after former President Donald Trump nominated her -- but also to hold those proceedings while Breyer is still sitting on the bench, according to two Democratic aides familiar with the matter.
Jackson was the first Black woman confirmed to an appellate court in a decade and is one of six Black female circuit court judges currently serving. She is also one of just 39 active Black female federal judges out of 793 total.
The 51-year-old also has some bipartisan appeal. She was confirmed 53-44 to her current seat in June 2021, drawing votes from three Republicans -- Sens. Lindsey Graham, R-S.C., Susan Collins, R-Maine, and Lisa Murkowski, R-Alaska. Collins told reporters Wednesday that Senate Judiciary Chairman Dick Durbin called her to discuss the path forward regarding a potential Supreme Court confirmation in the Senate.
At the time of Jackson's last confirmation, several Republican senators brought up the advocacy group Demand Justice, which has supported Jackson's nomination and has called for expanding the Supreme Court.
"Demand Justice claims that the Supreme Court is broken," Sen. John Cornyn, R-Texas, said. "Do you think the Supreme Court is broken?"
"Senator, I've never said anything about the Supreme Court being broken," Jackson said in response. "Again, I'm not going to comment on the structure, the size, the functioning even, of the Supreme Court."
Under questioning, she also characterized religious liberty as a foundational tenet of the U.S. government and said the Supreme Court has made clear that the government cannot infringe on religious rights.
She was also asked if she believed race would play a role in her decision making, if mandatory minimums were racist and the role of race in the judicial system.
Jackson repeatedly emphasized her belief in judicial independence.
Jackson grew up attending public schools in Miami and graduated from Harvard College. She has served as an assistant public defender and as vice chair and commissioner on the U.S. Sentencing Commission.
The mother of two teenage daughters is related to former House Speaker Paul Ryan by marriage.
Ryan testified on her behalf when she was nominated to the district court in 2012, offering his "unequivocal" endorsement.
During her circuit court confirmation hearing, she offered a poignant response when Sen. Alex Padilla, D-Calif., asked what the nomination meant to her.
"It is the beauty and the majesty of this country, that someone who comes from a background like mine could find herself in this position," she answered. "And so I'm just enormously grateful to have this opportunity to be a part of the law in this way, and I'm truly thankful for the president giving me the honor of this nomination."
ABC News' Lauren Lantry, Adia Robinson and Trish Turner contributed to this report.