Senator Mitch McConnell, the Kentucky Republican and minority leader, threatened on Monday to block any Supreme Court nominee put forward by President Biden in 2024 if Republicans regain control of the Senate next year.
“I think in the middle of a presidential election, if you have a Senate of the opposite party of the president, you have to go back to the 1880s to find the last time a vacancy was filled,” Mr. McConnell said in a radio interview with the conservative commentator Hugh Hewitt. “So I think it’s highly unlikely.”
His position is no surprise since it is in line with his refusal in 2016 to consider President Barack Obama’s high court nomination of Merrick B. Garland, now the attorney general, saying it was too close to the presidential election even though the vacancy occurred in February.
As for what would happen if a seat became open in 2023 and Republicans controlled the Senate, Mr. McConnell did not declare that he would prevent Mr. Biden from advancing a nominee, but left the door open to the possibility. “Well, we’d have to wait and see what happens,” said Mr. McConnell.
Stonewalling a nominee in the year before a presidential election would amount to a significant escalation in the judicial confirmation wars.
Mr. McConnell’s pronouncements will likely amplify calls from progressive activists for Justice Stephen G. Breyer to retire while Democrats still hold the Senate and can move through a successor. Justice Breyer, 82, an appointee of President Bill Clinton, has resisted calls to step aside. Justices often time their retirements to the end of the court’s term, which comes in two weeks.
On Sunday, even before Mr. McConnell’s statement, Representative Alexandria Ocasio-Cortez, Democrat of New York, joined those urging Justice Breyer’s retirement, saying on CNN that she was “inclined to say yes” to the question of whether the justice should leave the bench while Democrats were still assured of Senate control.
Mr. McConnell’s position in 2016 stood in stark contrast to last year when Senate Republicans, still in control of the Senate, rushed through the confirmation of Justice Amy Coney Barrett just days before the presidential election following the death in September of Justice Ruth Bader Ginsburg.
“What was different in 2020 was we were of the same party as the president,” Mr. McConnell told Mr. Hewitt. “And that’s why we went ahead with it.” Mr. McConnell also gave himself a pat on the back for the way he handled the Barrett nomination, saying that it “took a great deal of priority and, I think, skill to get Amy Coney Barrett through.”
He also again called denying Mr. Obama a third pick on the court “the most consequential thing I’ve done in my time as majority leader of the Senate.”
Mr. McConnell’s decision to block Mr. Obama from filling the vacancy caused by the death of Justice Antonin Scalia was widely credited with encouraging conservatives to rally around Donald J. Trump for the presidency, allowing Mr. Trump to ultimately name three justices to the court, which now has a 6-3 conservative majority.