A number of liberal-leaning judges have stepped aside since Joe Biden took office, and more are expected to do the same — including possibly the oldest member of the US Supreme Court — presenting the new president with an early test of his ability to make his mark on federal courts.

Throughout the federal judiciary, Democrats are nursing wounds inflicted by Mr Trump, whose swift work in installing judges to lifetime positions during his four years in office has transformed US courts for a generation.

Mr Trump appointed 54 appeals court judges during his four years in office, one fewer than Mr Obama’s total over eight years in office, according to the Pew Research Center. In total, Mr Trump appointed 234 federal judges, including 14 judges after he lost the November 3 election, according to an analysis by Russell Wheeler at the Brookings Institution, a think-tank.

Mr Biden now faces the challenge of trying to match Mr Trump’s success with judicial nominations. Failure to do so could deal a long-term setback to liberal causes from healthcare to financial regulation.

In the days since Mr Biden was sworn into office, 10 federal judges have already announced they have transitioned to “senior status”, a state of semi-retirement available to judges over the age of 65 that creates a vacancy on the bench, which Mr Biden can fill.

These include California district court judge William Alsup, an influential figure in some of Silicon Valley’s biggest courtroom battles, and Robert Katzmann of the 2nd US Circuit Court of Appeals in Manhattan.

At least 13 other judges have said they will step aside in the next 12 months, including three nominated by Republican president George W Bush. In total, there are 60 current and expected vacancies throughout the federal judiciary.

A seat on the influential DC Circuit Court of Appeals currently held by Merrick Garland — whose nomination to the US Supreme Court by Barack Obama was stymied by the Republican-controlled Senate — will also open up if he is confirmed as Mr Biden’s attorney-general.

Expected judicial retirements during Mr Biden’s first term could possibly include at least one member of the Supreme Court, which would give the president his first chance at adding a new liberal justice to the high court.

Some Democrats were critical of Ruth Bader Ginsburg’s decision not to retire while Barack Obama was in the White House and Democrats controlled the Senate, which gave him the votes to replace her with another liberal judge. She died during Mr Trump’s final months in office, and he replaced her with a conservative, Amy Coney Barrett, who was confirmed just nine days before the presidential election.

Now that Mr Biden is in the White House, all eyes are on Stephen Breyer, a member of the court’s liberal wing who at 82 is the oldest person on the Supreme Court. The Democrats’ slim Senate majority could give Mr Biden the votes he needs to confirm a replacement should a vacancy arise.

“I would not be surprised at all to see Justice Breyer retire this June,” said Adam Winkler, a law professor at UCLA who formerly clerked for an appeals court judge.

For the rest of the federal courts, “we are likely to see a number of additional retirements in the near future” as older, liberal judges step down now that a Democrat is back in the White House, he said.

To accelerate judicial nominations, Mr Biden’s team in December sent a letter to Democratic senators asking them to quickly recommend potential candidates to the White House.

In January, the Biden team named Paige Herwig to help with judicial nominations. She had done similar work for the Obama administration and the Senate judiciary committee, and liberal justice groups cheered her appointment.

Some Democrats are nervous that a delay in nominating judges and moving them quickly through the Senate confirmation process could blunt Mr Biden’s ability to rebalance the courts.

“One of the huge problems that delayed President Obama’s nominees was waiting for senators [to make judicial recommendations],” Christopher Kang, who worked on judicial nominations in the Obama White House and now serves as chief counsel at the advocacy group Demand Justice, said at a Brookings Institution event.

Though Mr Biden has not yet nominated any judges, he has said he wants more diverse individuals on the bench. On the campaign trail, he said he would like to appoint first black woman to the Supreme Court.

One judge who would fit that bill is Ketanji Brown Jackson, a US district court judge in Washington, who was reportedly under consideration for the Supreme Court during the Obama administration. She is likely to be considered to replace Mr Garland on the Washington appeals court, which could provide a springboard to the high court when a seat is open.

Mr Trump also appointed some unusually young judges to these lifetime positions. In November, the Senate confirmed 33-year-old Kathryn Kimball Mizelle to be a district court judge in Florida.

“Biden will be under a lot of pressure to nominate reasonably useful people who can expect to be on the courts — like the Trump judges — for 30 or 40 years,” Mr Winkler said.

With the slimmest possible majority in the Senate, one recalcitrant Democrat could derail confirmation of Mr Biden’s judicial picks, said Sam Erman, a law professor at the University of Southern California, who clerked for Mr Garland and two Supreme Court justices.

“The real danger is one senator gets sick and can’t vote and the whole process gets stalled,” Mr Erman said. “He can’t afford to lose a single vote.”