Sen. Lindsey Graham, the South Carolina contortionist, illustrates the perils of attempted cleverness by people with negligible aptitude for it. He says that the principle he enunciated in 2016 and reaffirmed in 2018 — that he would not support confirming a Supreme Court nominee in the last year of President Donald Trump’s term — has expired. One reason he gives is — really — that Democrats in 2013 ended filibusters for circuit-court nominees.

The pandemic of national cynicism that the likes of Graham exacerbate is engulfing the Supreme Court, an institution whose functioning will be especially damaged by it. Immediately after Justice Antonin Scalia’s death in February 2016, Senate Republicans concocted a principle in order to give a patina of high-mindedness to something they were determined to do anyway. Now, for the same purpose, they have concocted a codicil that essentially nullifies the principle.

In 2016, slathering on populist rhetoric (about “the American people” having a “voice”), they proclaimed that no Supreme Court nominee should be confirmed in a presidential election year. Now they assert, without pretending to have an argument: Oh, never mind, because unlike in 2016, the Senate majority and the president are of the same party.

Many conservatives, lacking the conservative virtue of prudence, belabor the obvious with a sense of intellectual achievement: They say Barack Obama had the power to nominate Merrick Garland to replace Scalia, and the Senate had the power to deny him an up-or-down vote, so nothing more need be said.

Indeed, nothing more — if there is nothing more to constitutional etiquette than this cold logic of formal powers. The logic is as clear as it is obtuse when offered as a sufficient justification for not voting on an accomplished moderate jurist nominated 237 days before the 2016 election. But the nation’s often ferocious political competition, although framed by the Constitution, should be lubricated by prudence, whereby ferocity is tempered by a statesmanlike refusal to exercise every power the Constitution grants.

Sixteen Republicans who were in the Senate in 2016 and who are seeking reelection this year said (Susan Collins did not say this) that refusing to confirm a new justice during a presidential election year was high statesmanship.How many will have the effrontery to vote for someone nominated while presidential voting is underway, or after the election even if the nominator loses?

Republican senators correctly say that Senate Democrats, given a comparable opportunity, would behave with identical loutishness. Most Republicans argue, like kindergartners, that this justifies their behavior. But if just four non-plastic Republican senators do notignore their caucus’s pretended 2016 principle, the coming nominee cannot be confirmed before the election. And if Trump loses, perhaps even this amazingly malleable Republican caucus might not confirm his nominee before Joe Biden’s inauguration. So, whomever Trump nominates might be about to have a tortuous Merrick Garland experience of disappointment.

Suppose, however — not altogether implausibly — that the Republican Senate caucus is incapable of embarrassment. Suppose Biden wins and Democrats have a net gain of at least three Senate seats. And suppose that either before the election, or before the new Senate is sworn in on Jan. 3, Republicans confirm a new justice. And suppose Senate Democrats, spurred by their party’s enraged base and enabled by their quick abolition of the filibuster, enlarge the Supreme Court by at least four members (two fewer than Franklin Roosevelt envisioned).

This would erase the principal achievement — three Trump nominees — for which Senate Republicans, during four years of canine obedience to the nominator, have rationalized shedding their dignity and shredding their reputations. This institutional vandalism by Democrats would be a grievous injury to the court, which has, so far, largely escaped being drenched by the Niagara of public contempt for the great institutions of national governance, not least Congress. Public confidence in the court’s disinterestedness is the source of its power to defend the Constitution from willful and imprudent majorities, including Senate majorities.

Confidence in the court is as perishable as the reputations of the senators of both parties who in the next few years might cause the court to be seen as just another scuffed and soiled plaything in the nation’s increasingly tawdry political game. If so, the Republicans among those senators will be able to see the monument to their careers when they look east from the Capitol’s Senate wing, across First Street NE, to the court’s glistening white building, where a liberal majority will be presiding on a lengthened bench for a long time.