WASHINGTON — When President Trump took office, more than 100 vacancies for him to fill existed on the federal bench, an inaugural gift from Senate Republicans who persistently thwarted the Obama administration’s best efforts to install judges after Democrats lost control of the Senate in the 2014 elections.
Mr. Trump and Senator Mitch McConnell of Kentucky, the majority leader, are now furiously installing conservatives in those openings, aiming to deny the next president the same opportunity to remake the courts should a Democrat defeat Mr. Trump next year.
But liberal activists, hoping for a chance to offset the growing conservative presence in the courts, have identified a pool of potential judicial vacancies that could remain out of Mr. Trump’s reach — scores of seats held by veteran judges appointed by Democrats who may be biding their time, awaiting the outcome of the 2020 presidential race.
Nearly 100 federal judges nominated by Presidents Barack Obama and Bill Clinton — and even Jimmy Carter — would be eligible to take semiretirement by the time the next president is inaugurated, a status that allows them to continue to preside over cases but creates an official vacancy that could be filled by a presumably younger full-time replacement.
Anticipating that at least some of those long-serving judges named by Democrats would step aside once a president more to their ideological liking took office, liberal judicial activists have begun a new effort to recommend possible successors who could immediately be funneled into the judicial pipeline. Those successors would not shift the ideological balance of the courts, but like Mr. Trump’s young conservatives, they would have staying power.
“It is essential to be ready on Day 1 of a new administration with names to fill every vacancy,” said Nan Aron, the president of the Alliance for Justice, the 40-year-old liberal judicial advocacy group. “This is to start identifying people so the new president won’t waste a minute in addressing this need.”
The initiative is called Building the Bench, and the Alliance for Justice is being joined in underwriting and supporting it by a number of other liberal advocacy groups and labor unions. A group of more than 30 law professors and lawyers will serve as an advisory board.
The progressive organizations and individuals have traditionally weighed in on judicial nominations and the confirmation process when Democrats were in the White House, but this represents a much more concerted effort than in the past.
It reflects both what the left sees as an escalating crisis because of the success of the Trump judicial assembly line as well as an acknowledgment of the benefits his administration reaped by having a list of potential Supreme Court justices in hand before Mr. Trump was even sworn in. The list of candidates was critical to Mr. Trump’s securing conservative backing, but it also enabled the administration to rapidly fill not only a Supreme Court seat but a number of important appeals court posts with judges who had been approved and vetted by conservative activists.
“The impetus for this is to start repairing the harm this administration has done to the federal bench,” Ms. Aron said of the new project.
The liberal groups also unhappily remember a relatively slow start to the judicial nominating process by Mr. Obama’s administration given its need to focus on the faltering economy and other issues. That forced the White House to try to make up ground later, only to run into a Republican-controlled Senate.
Unlike the unprecedented Trump list, the liberal groups do not intend to make their recommendations public — they see them more as a guide for a potential Democratic administration. The idea is to look at district and appellate courts that could experience a rush of retirements after the election and find suitable successors for anyone who leaves.
Those involved in the effort say a main focus will be on identifying potential candidates who could diversify the nominees for the federal bench beyond the usual categories of sitting judges, prosecutors and senior law partners — potentially including public defenders, civil rights advocates and others with more varied backgrounds.
“It would be nice to see more people who have experience outside the three big pots,” said Peter Shane, a constitutional law professor at Ohio State University and a member of the Building the Bench advisory committee.
Of course, there is no certainty that the veteran judges who had been placed on the bench by Democrats are interested in leaving. But politically strategic retirements are hardly unheard-of at either the Supreme Court or lower court level. It would only make sense that a judge would like a successor to share some common ground and legal view.
Just last week, Mr. McConnell said in a Fox News interview that he doubted any of the four members of the Supreme Court nominated by Democrats would quit the court while Mr. Trump was in the White House — outside of what Mr. McConnell called “a significant life-ending event.”
Russell Wheeler, a judicial expert at the Brookings Institution, noted that it was risky to apply motives to why a judge would or would not quit at a certain point, but that the politics of succession would have to be a factor.
“Clearly they hold all sorts of reasons, but one of them has to be from the Democratic side that I would just as soon have Joe Biden or Kamala Harris appoint my successor as Donald Trump,” Mr. Wheeler said.
That tendency is reflected in the fact that many more Republican-nominated judges than those put forward by Democrats have taken senior status or left the bench entirely since Mr. Trump was elected in 2016.
Under a formula that is based on age and years on the bench, Mr. Wheeler estimates that 35 Democrat-appointed appeals court judges are now eligible for senior status, a number that could grow to 39 by Election Day 2020. Among district court judges, 53 appointed by Democrats are now eligible, with the potential to grow to 58. And some Republican-appointed judges out of the 100 now eligible for senior status might prefer not to be replaced by Mr. Trump, as well, expanding the possible field of post-2020 vacancies.
Whether a Democratic presidential victory in 2020 would prompt a flurry of judicial retirements remains to be seen. And, of course, a Democratic president may have to contend with a Republican-controlled Senate, which would be a factor in how effective a Democratic administration could be in replacing judges. But the liberal advocacy groups intend to be much more prepared for the prospect than in the past.
At the same time, a victory by Mr. Trump could provide him a spate of new vacancies to fill if those judges who may have been putting off retirement decide four more years is just too long to wait.