The Supreme Court is considering whether to take up the question of presidential immunity — that is, the idea that a president, by virtue of the unique nature of the office, is entitled to exceedingly broad protections from legal consequences for statements made and actions taken while in office. If the court takes up that question in a case regarding Donald Trump, it will have profound consequences for both the 2024 election and the bigger question of presidential power.

To advance the Jan. 6 case against Mr. Trump, the special counsel Jack Smith wants to skip a step at the appellate court and have the Supreme Court rule on that critical question, since a ruling in Mr. Trump’s favor would end the case. A protracted delay could have the same effect, preventing the trial from happening before the election and allowing Mr. Trump to call off the prosecution if he wins. (The court might also be asked about presidential immunity in a civil context, after the D.C. Circuit rejected immunity arguments from Mr. Trump.)

The court should rule on the question of presidential immunity, and it should do so on an accelerated timetable. The Supreme Court’s decision could not only affect the likelihood that Mr. Trump will stand trial before the 2024 election; it could also send important signals about whether the court will stand as a bulwark against some of the most extreme assertions of executive authority if Mr. Trump is given a second term.

In that sense, this case involves not just potential accountability for Jan. 6 but also whether and how the law and the courts will treat Mr. Trump if he returns to office — as well as future holders of that office.

Not surprisingly, Mr. Trump has staked out an absolutist position. Stripped to its essentials, his argument in both the criminal and civil cases pending against him is Richard Nixon’s syllogism: “When the president does it, that means that it is not illegal.”

Recent experience makes clear that the justices are more than capable of moving quickly if they deem a case sufficiently urgent: “certiorari before judgment” was once rare, but the court has been more than willing to allow parties to leapfrog the appellate courts in recent years. The law professor Steve Vladeck counts 19 times the court has granted such petitions just since 2019.

Yesterday, the D.C. Circuit signaled its interest in a speedy resolution of the immunity question, scheduling oral arguments for Jan. 9. The Supreme Court need not await that court’s decision before acting — but whether it schedules arguments before or after the D.C. Circuit has made its decision, it is critical that the court not delay.

If it commits to moving quickly, the court can address the question of presidential immunity on a timeline that will either facilitate or prevent a trial and verdict in the criminal case before voters head to the polls and perhaps even before the Republican Party has selected its presidential nominee. (The court should also accelerate its review of a case related to Jan. 6 that it agreed to hear last week, involving a charge against a man convicted of obstruction of an official proceeding. That charge is also at issue in two of the counts against Mr. Trump, so the case has obvious implications for Mr. Trump’s trial and verdict.)

The idea of presidential immunity has always existed uneasily with the American constitutional tradition. As Judge Tanya Chutkan’s opinion in the Jan. 6 criminal case noted, Alexander Hamilton, a defender of a muscular executive, emphasized the difference between king and president, writing that for a king, “there is no constitutional tribunal to which he is amenable; no punishment to which he can be subjected.” A president, by contrast, enjoys no such blanket protections.

Nevertheless, courts and the executive branch have fashioned a doctrine of presidential immunity, using largely pragmatic reasoning — grounded not in constitutional text or history but in the needs and demands of the contemporary presidency — to construct a set of protections that attach to the president under certain circumstances.

In 1974 in United States v. Nixon, the Supreme Court made clear that no constitutional principle supported “an absolute, unqualified presidential privilege of immunity from judicial process under all circumstances.” But the court concluded that certain pragmatic and structural principles — the need for presidents to receive candid advice from advisers, the importance of protecting each branch from encroachment by the others — supported the existence of a qualified presidential ability, usually known as executive privilege, to protect certain information from compelled disclosure.

A second case in this line, Nixon v. Fitzgerald, had to do with a civil lawsuit filed by a former federal employee against Mr. Nixon, alleging that as president, he had been involved in the employee’s unlawful firing. The court in that case announced an absolute immunity against civil damages liability for the president’s official acts. Explaining that the constant fear of lawsuits could “distract a president from his public duties,” to the detriment of the president, the office and the country, the court found that immunity was “a functionally mandated incident of the president’s unique office.”

Still, the court explained, this immunity extended only to conduct within the “outer perimeter” of the president’s official responsibility — that is, the immunity did not cover purely private or unofficial conduct.

If the fractured opinion in Fitzgerald left some questions open, the Supreme Court in Clinton v. Jones (involving Bill Clinton) made clear that the president is not beyond the reach of the law, in particular when the conduct at issue is unofficial — in that case, predating the presidency. The court, rebuffing Mr. Clinton’s efforts to delay Paula Jones’s sexual harassment lawsuit until after his presidency, was unmoved by the prospect of interference with and distraction from presidential duties. Requiring a sitting president to participate in civil litigation growing out of prepresidential conduct, the court reasoned, did not “rise to the level of constitutionally forbidden impairment of the executive’s ability to perform its constitutionally mandated functions.”

In 2020 a 7-to-2 majority in Trump v. Vance rejected Mr. Trump’s argument that he should not have to cooperate with a subpoena in a state criminal case. And the court was unanimous in rejecting Mr. Trump’s arguments for absolute immunity.

Each of these cases identified reasons for limiting the availability of certain kinds of legal process in the case of sitting presidents and, in some cases, ex-presidents. But none came close to announcing the sort of absolute freedom from judicially enforced accountability that Mr. Trump now seeks.

Beyond these cases, the Department of Justice’s Office of Legal Counsel has taken the position that a sitting president is immune from federal criminal prosecution. But the department emphatically does not believe that the logic of its position extends the same immunity to ex-presidents.

Executive branch practice confirms this view. When Gerald Ford pardoned Mr. Nixon, the language of his proclamation presupposed that Mr. Nixon was eligible for prosecution for his conduct while president. It noted that “as a result of certain acts or omissions occurring before his resignation from the office of president, Richard Nixon has become liable to possible indictment and trial for offenses against the United States.” And Mr. Ford’s “full, free and absolute pardon” encompassed any offenses that Mr. Nixon “committed or may have committed or taken part in during the period from Jan. 20, 1969, through Aug. 9, 1974” — that is, precisely the period of his presidency.

In light of all of this precedent, the lower courts considering Mr. Trump’s immunity arguments found them relatively easy to dispose of. In the criminal case, Judge Chutkan made clear that the court’s precedents and basic constitutional logic establish that Mr. Trump’s status as an ex-president does not “bestow on him the divine right of kings to evade the criminal accountability that governs his fellow citizens.”

In the civil case, brought by a group of former Capitol Police officers and members of Congress who suffered harms on Jan. 6, an ideologically diverse panel of the D.C. Circuit — which included Judge Gregory Katsas, who was appointed by Mr. Trump and worked in his White House Counsel’s Office — concluded that the absolute immunity announced in Fitzgerald did not require the immediate dismissal of the civil suit against Mr. Trump.

For a Supreme Court that holds itself out as hewing closely to text, history and tradition, immunity should present an easy case, and Mr. Trump should lose. There’s nothing in the Constitution’s text that confers immunity on the president (and the document explicitly creates other sorts of immunities). And neither our history nor our traditions support presidential immunity in cases like these.

If the court nevertheless distorts precedent and principle to endorse some version of Mr. Trump’s logic — or if it facilitates a delay that has functionally the same result — it will have revealed the hollowness at the core of its professed method and expose itself as willing to act in the most craven ways to advance the electoral prospects of the leading Republican contender.

It will also send a chilling message that Mr. Trump may be able to carry out some of what he appears poised to do in a second term — pursue political enemies, abuse the Insurrection Act, decimate the civil service — emboldened by the knowledge that the Supreme Court will stand as no obstacle.