WASHINGTON — Senate Democrats say they plan to move speedily to consider President Biden’s nominee for the Supreme Court vacancy created by the retirement of Justice Stephen G. Breyer, following the lead of Republicans who raced through the nomination of Justice Amy Coney Barrett in a matter of weeks before the 2020 elections.
Holding a bare 50-seat majority that is under severe threat in November’s midterm elections, Democrats acknowledged the need to act fast, particularly since an illness or death of one of their members could deprive them of their numerical advantage and greatly complicate efforts to fill the seat.
“President 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,” Senator Chuck Schumer, Democrat of New York and the majority leader, said on Wednesday after plans for Justice Breyer’s departure became public.
Democrats could confirm a successor to Justice Breyer without any Republican support under Senate rules that shield a Supreme Court nomination from a filibuster, but they must remain firmly united to do so.
With the Senate evenly split, Vice President Kamala Harris could be called upon to break a tie vote over any nominee, giving Democrats the upper hand as long as all of the members who usually vote with them rally behind whomever the president chooses.
But even with the numbers and the rules working in their favor, Democrats are well aware that they have a narrow path and that plans could go awry. They are wary of Senator Mitch McConnell, Republican of Kentucky and the minority leader, who has previously bedeviled Democrats on high court fights and is known for finding novel ways to use the chamber’s rules to his advantage, even when they appear stacked against him.
Mr. McConnell is generally eager to use any means at his disposal to delay or derail Democrats’ best-laid plans, particularly when it comes to the Supreme Court. In 2016, he summarily blocked President Barack Obama’s nominee, Merrick B. Garland, citing the presidential election 10 months off. He then pushed Justice Barrett through at President Donald J. Trump’s urging in the days before the 2020 election.
As they assessed the coming fight, Democrats predicted on Wednesday that Republicans would throw up procedural roadblocks and arguments in an effort to slow the process and sink a nominee they are likely to consider too liberal.
But leading Republicans conceded that Democrats could seat a new justice on their own, if necessary.
“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,” Senator Lindsey Graham of South Carolina, a senior member of the Judiciary Committee, said in a statement.
If any Senate Democrat broke from the party on the nomination — as Senators Joe Manchin III of West Virginia and Kyrsten Sinema of Arizona have on major policy issues in the Biden era — it could endanger the president’s pick and provide cover for Republicans to be in opposition as well. But despite splits on some policy issues, Democrats have so far supported the judicial candidates the Biden administration has put forward.
Mr. McConnell did not weigh in on Wednesday with his views on the coming vacancy, telling the news media in Kentucky that he would await a formal announcement from Justice Breyer. He said it was too early to know what his party’s response would be.
“We don’t even know who the nominee is yet,” Mr. McConnell said.
The Judiciary Committee has been preparing for a potential Supreme Court showdown since Democrats took over the Senate a year ago and Senator Richard J. Durbin, Democrat of Illinois, became the committee’s chairman.
Senate officials said the 11-11 split on the panel because of the evenly divided Senate could create difficulties of its own and that research was already underway on how to address some potential problems, such as making sure Republicans are not able to block action by refusing to participate.
Though he has long experience on the panel and has participated in multiple Supreme Court showdowns, this would be Mr. Durbin’s first time overseeing a confirmation.
“With this Supreme Court vacancy, President Biden has the opportunity to nominate someone who will bring diversity, experience and an evenhanded approach to the administration of justice,” Mr. Durbin said, promising to “expeditiously” move the nominee through the committee.
Democrats, relieved that Justice Breyer was stepping down while they still controlled the Senate, called on Mr. Biden to follow through on his promise to nominate the first Black woman to the court.
“I trust President Biden to move forward an exceptional nominee who will uphold all American’s rights and liberties — including protecting voting rights and reproductive rights,” said Senator Patty Murray of Washington, the No. 3 Democrat. “I am ready to move as quickly as possible to consider and confirm a highly qualified nominee who will break barriers and make history as the first Black woman on the Supreme Court of the United States.”
Mr. Schumer wants the entire process to take weeks, not months, according to a person familiar with his thinking who spoke about it on the condition of anonymity.
Presidents have historically taken anywhere from days to months to make a nomination to the Supreme Court after a vacancy occurs. Justice Breyer is preparing to retire at the end of the Supreme Court term in June, but Democrats plan to begin the process of confirming a nominee to succeed him as soon as Mr. Biden announces a candidate. The new justice could then be seated shortly after Justice Breyer officially steps down, the person familiar with Mr. Schumer’s thinking said.
Given the current level of political polarization, only a handful of Senate Republicans are likely to be in play as potential supporters of the president’s nominee.
Many Republicans in the Senate have, as a matter of course, opposed Mr. Biden’s nominees for seats on the lower federal courts, portraying them as too progressive. The intense spotlight of a Supreme Court nomination — and the importance Republican voters traditionally place on the court — will make drawing support from across the aisle even tougher for the president.
Just three Republicans — Senators Lindsey Graham of South Carolina, Susan Collins of Maine and Lisa Murkowski of Alaska — voted in June to confirm Judge Ketanji Brown Jackson, who is considered a front-runner to succeed Justice Breyer, to the U.S. Court of Appeals for the District of Columbia Circuit.
But backing someone for an appeals court post does not guarantee the same level of support for a high court vacancy. Multiple senators have voted against Supreme Court nominees they had previously backed.
Ms. Murkowski, a centrist Republican who is seeking re-election this year, has previously gone her own way on high court nominations, opposing Mr. Trump’s choice of Justice Brett M. Kavanaugh in 2018 but backing his nomination of Justice Barrett. Ms. Collins, another closely watched senator on Supreme Court nominations, voted to confirm Mr. Kavanaugh but opposed Ms. Barrett.
In a statement issued Wednesday, Ms. Collins praised Justice Breyer but said nothing beyond that.
Mr. Biden’s pledge to make history by seating the first Black woman on the Supreme Court could conceivably influence the votes of Republicans who want to be counted as supporters of diversifying the court.
But many Republicans — including some on the Judiciary Committee who are considered possible future presidential candidates — will be looking to use the confirmation fight to send a signal to Republican voters about their views on who belongs on the high court, and who does not.
“I predict that Chuck Schumer and whoever is running the White House will force all Democrats to obey and walk the plank in support of a radical liberal with extremist views,” said Senator Rick Scott of Florida, the chairman of his party’s Senate campaign arm.
Luke Broadwater and Emily Cochrane contributed reporting.