The nearly three hours of oral argument in Trump v. United States demonstrates that the 45th president’s bid for immunity is far from frivolous. It’s no lead pipe cinch, but it could carry the day. If it does, future presidents will have Mr. Trump to thank for protecting their office. In the meantime, we can’t help but be impressed by what appears to be the court’s caution. We imagine Madison following with appreciation. 

The court’s liberal justices got in their points with respect to Mr. Trump’s position that former presidents are entitled to “absolute immunity” for all of their official acts. Justice Ketanji Brown Jackson darkly warned of an Oval Office transformed into a “seat of criminality.” DOJ’s man in court, Michael Dreeben, foresees “bribery, treason, sedition, murder” if Mr. Trump’s argument wins the day. Naturally, a despot was invoked.

The court’s conservative cohort voiced a different species of worry — for the presidency. Justice Samuel Alito appeared doubtful of Mr. Dreeben’s contention that political prosecutions could be forestalled by grand juries. Those tribunals, the justice chuckled, would indict a ham sandwich. Justice Neil Gorsuch asked if a conversation between president and vice president could be criminal. That stumped even the adroit Mr. Dreeben. 

Even if the Nine turn out to be unpersuaded by Mr. Trump’s advocate, John Sauer, that denying his client’s brand of immunity would “end the presidency as we know it,” they still appear likely to frustrate Special Counsel Jack Smith’s all-fired rush to trial. The most illuminating moment in that respect was a colloquy between Mr. Sauer and Justice Amy Coney Barrett, which could be the exchange that reshapes the case and brings it into sharper focus.

Justice Barrett elicited from Mr. Sauer that even Mr. Trump concurs that the protections of the presidency do not cover purely “private acts.” The attorney even conceded that some of the actions alleged by Mr. Smith, if true, would not be covered. The sticking point is so-called “official acts.” That is where Mr. Trump claims absolute immunity, and Mr. Smith contends that criminal law applies, save for “core” presidential functions like pardons. 

The rub is that the division between private acts and official ones in respect of Mr. Trump has yet to be litigated. Now Mr. Smith could decide that the juice is not worth the squeeze, and edit his indictment to avoid what the court in Nixon v. Fitzgerald called the “outer perimeter” of the duties of the chief executive. Such an outcome might not deliver a Richter-scale ruling, but the presidency has survived this long without one.

Listening to the arguments today, though, we couldn’t shake the notion that this drama could come down to the Chief Justice. He marked a point when he posed this question. Let’s “say the official act is appointing ambassadors, and the president appoints a particular individual to a country, but it’s in exchange for a bribe.” What then, he asked? Mr. Sauer allowed that the bribe would be “private conduct.”     

No one was suggesting that Mr. Trump took bribes. It’s clear, though, that the Chief Justice is into the particulars. It leaves us wondering whether the Chief Justice and his colleagues will decide to send the matter back to Judge Chutkin’s court to go over each relevant charge to see which involved acts that were official and which were private. That would suggest that at least one court takes the uniqueness of the presidency seriously.