WHEN Republicans vowed to stonewall Barack Obama’s Supreme Court nominee in February, Donald Trump was still a longshot to win the Republican nomination. Nearly six months later, Mr Trump is the nominee and looks poised to deliver a devastating loss for the Republican Party in the presidential election. With a victory for Hillary Clinton looking increasingly likely, Senate majority leader Mitch McConnell is, for now, standing by his promise to let the next president choose Antonin Scalia’s successor. But many think Mr McConnell and the Judiciary Committee chair, Senator Charles Grassley, would renege on their pledge after Mrs Clinton had won the White House in November. Fearing that she would pick a new nominee—somebody younger and more liberal than Mr Garland, a 63-year-old moderate—the party might quickly confirm Mr Garland in Mr Obama’s last two months in office, or so one conventional take has it. It would not be shocking for Republicans to reverse themselves on the no-hearings-no-vote pledge. In the course of his campaign, Mr Trump has shown how little political cost comes with repeatedly disavowing one’s previous positions. (His slump in the polls seems more attributable to criticising the parents of a fallen American Muslim soldier than to any particular flip-flop.) But there is still good reason to doubt the theory of a late-autumn, lame-duck-session Garland confirmation, and it has everything to do with how Republicans view their opportunities a few years down the road.

Partisans on both sides are saying that the next president could appoint as many as four Supreme Court justices. Each of the four most recent presidents has seated two justices, so having the chance to name four would give the next president an outsize influence on the shape of American law for generations to come. But here’s the thing: the next president will not, in fact, have more than a ray or two of hope of naming four justices. Yes, three of the justices are getting up there: Ruth Bader Ginsburg is 84, while Stephen Breyer and Anthony Kennedy are close behind at 78 (next week) and 80, respectively. (The fourth-oldest justice, Clarence Thomas, is only 68.) But these elderly jurists are nimble of both mind and body, and only Ruth Bader Ginsburg, a two-time cancer survivor, has had serious health concerns. Consulting the actuarial tables, Oliver Roeder of FiveThirtyEight calculates that there is only a 9.7% chance of four vacancies (in addition to Mr Scalia’s) over the next eight years; odds are there will be only two. And in the next four years, he reckons, there’s about a 40% chance of a single vacancy and a 32% chance of none at all.

Given these more realistic expectations, there are a host of reasons Republicans may hesitate to give the nod to Mr Garland before Mrs Clinton takes office next January, should she defeat Mr Trump in November.

Here is one: the moment Mr Garland fills the ninth seat, the 4-4 ideological split on the court would open into a 5-4 divide in the liberals’ favour. The longer that can be delayed, from Republicans’ point of view, the better. Awaiting a new administration and Senate for confirmation hearings next January means Mr Garland would not don the black robes until at least March, and probably April, when the term’s oral arguments will be all but wrapped up. A Justice Garland would play almost no role on the court until the next term begins in October 2017.

Second, the Republican Party is unlikely to be baited by Mrs Clinton’s hedges when asked whether she, as president, would stick with Mr Obama’s nominee. Plainly, in Republican eyes, Mr Garland is preferable to a younger, more liberal nominee with the potential to serve decades on the court. But Mr McConnell knows that even if the Democrats win the Senate, they will not have a filibuster-proof, 60-seat majority that would be hospitable to a far-left pick. That means Mrs Clinton is very unlikely to push for anyone too far to the left of Mr Garland. Given the eminent qualifications and decency of Mr Obama’s choice, it seems unlikely she would abandon him—and Mr McConnell knows it.

Third, if Mrs Clinton defies that prediction and nominates someone like Goodwin Liu, a judge deemed too liberal by Republicans when Mr Obama nominated him to the 9th Circuit Court of Appeals in 2010 (he withdrew after incurring Republican Party opposition), the only way she would get him into Mr Scalia’s old seat is by persuading Senate Democrats—assuming they control the chamber—to expand the so-called “nuclear option” they first resorted to in 2013. That year, in the face of Republican intransigence on several lower-court judicial appointments, then-Majority Leader Harry Reid held a vote to permit the confirmation of judicial and executive-office nominees by a simple majority vote rather than a supermajority of 60. Upending Senate rules again to eliminate the filibuster for Supreme Court nominations is certainly not out of the question, but it is a sword that cuts both ways and, again, Mr McConnell knows this. The opposition party typically does well in midterm elections. So if the Democrats win the Senate in 2016, they could well lose the majority again in 2018, permitting the Republican Party to hold any Supreme Court nominees hostage in the second half of Mrs Clinton’s first term. And if the GOP succeeds in making Mrs Clinton the first one-term president since George Bush the elder, its 2020 nominee may leave a greater mark on the Supreme Court than did America’s first female president.

There is an excellent reason why the Senate should do its constitutional duty and hold hearings for Merrick Garland right now: with only eight justices, the Supreme Court has shown it cannot live up to its role as the final arbiter on conflicts of American law. Unfortunately, there doesn’t seem to be any partisan or strategic impetus for Senate Republicans to consider Mr Garland before Mr Obama leaves office.