WASHINGTON – President Donald Trump pressed Senate Republicans on Saturday to confirm his choice to replace Justice Ruth Bader Ginsburg “without delay,” setting up a momentous battle sure to inflame the campaign even as party leaders weighed whether they could force a confirmation vote before the election Nov. 3.

Trump appears likely to nominate a successor to Ginsburg this week after her death Friday — a selection that, if confirmed, would shift the Supreme Court to the right for years. But with some Republican senators balking, Sen. Mitch McConnell, the majority leader from Kentucky, was canvassing to figure out whether he had enough votes to rush a confirmation in the next six weeks.

“We were put in this position of power and importance to make decisions for the people who so proudly elected us, the most important of which has long been considered to be the selection of United States Supreme Court Justices,” Trump wrote Saturday morning on Twitter. “We have this obligation, without delay!”

It was not immediately clear whether Trump would push ahead with the gamble of a Senate showdown before the election that would cement his legacy or wait to confirm a choice in a lame-duck session that would follow the election. Some Republican strategists said it would make more sense for the president to name a choice right away and proceed with hearings but wait for a Senate vote until after Nov. 3 to give Republicans who have soured on Trump because of the coronavirus pandemic or other reasons an incentive to turn out to vote.

McConnell moved to stave off defections in his conference by sending a letter late Friday to Republican senators urging them to “keep your powder dry” and not “prematurely lock yourselves into a position you may later regret.” At least two Republicans have made clear that they would not support jamming through a nominee so close to a presidential election, meaning McConnell, with a 53-47 majority and Vice President Mike Pence as a tiebreaker, could afford to lose only one more.

But some Republicans — like Sen. Ted Cruz of Texas — were agitating for a quick vote, arguing that a potentially messy pandemic election with the president already challenging the legitimacy of mail-in voting could wind up at the Supreme Court much as the 2000 election did. A shorthanded eight-member court could deadlock at 4-4 if Chief Justice John Roberts sided with the three remaining liberals, as he has on a few occasions, whereas another Trump-appointed justice would cement the conservative hold on the bench.

“We cannot have Election Day come and go with a 4-4 court,” Cruz said Friday night on Fox News. “A 4-4 court that is equally divided cannot decide anything. And I think we risk a constitutional crisis if we do not have a nine-justice Supreme Court, particularly when there is such a risk of a contested election.”

Beyond any legal challenges that may stem from the 2020 election, the next pick could shape important decisions on abortion and the Affordable Care Act, among other issues.

No vacancy at the Supreme Court occurring so close to a presidential election in U.S. history has been filled by Senate vote before the election. The closest came in 1916 when Chief Justice Charles Evans Hughes resigned 150 days before the election to run as the Republican candidate, and his successor was confirmed before the balloting.

When a retirement opened up a seat right before the 1956 election, President Dwight D. Eisenhower filled it with a recess appointment, reaching across the aisle to install a Democrat, William J. Brennan. After winning a second term, Eisenhower formally nominated Brennan for the lifetime position. The recess appointment was not controversial at the time, and Brennan was eventually confirmed with almost no opposition.

For today’s partisans, the more memorable precedent was Justice Antonin Scalia’s death in February 2016, which came 269 days before the election. McConnell blocked President Barack Obama from filling the seat with his nominee, Judge Merrick Garland, arguing that it was too close to the election.

“The American people should have a voice in the selection of their next Supreme Court justice,” McConnell said in a statement released after Scalia’s death. “Therefore, this vacancy should not be filled until we have a new president.”

McConnell later amended his rationale, saying it was not just proximity to the election that justified blocking a nominee but the fact that the president and the Senate majority at the time were held by opposite parties. Still, after Ginsburg’s death Friday, Democrats, led by former Vice President Joe Biden, their presidential nominee, demanded that Republicans respect the precedent they set of not acting so close to a presidential election — in this case much closer — and threw McConnell’s words back at him.