It is one of the ironies of the trial of President Trump on a charge of incitement of insurrection that the speech most likely to be studied by historians is that delivered after the verdict — not guilty — was brought in. It was after the Senate ordered the outcome be sent for safekeeping with the Secretary of State, and the court of impeachment was adjourned, that Senator Mitch McConnell unloaded.

His speech is likely to go down as one of the most remarkable ever delivered in the Senate. It was a constitutional highwire act worthy of the Great Wallenda. And, not to put too fine a point on it, it might well prove to be more damning to Mr. Trump than anything said by the prosecution — more damning, even, than a guilty verdict from the Senate would have been, though that can be but guesswork.

Mr. McConnell had just finished voting to acquit a former president he has clearly come to detest. He evidently felt that he had to say something to justify, or explain, that decision. So he opened with a five-word sentence. “January 6th,” he said, “was a disgrace.” Americans “attacked their own government,” “used terrorism to try to stop a specific piece of domestic business they did not like,” and “beat and bloodied our own police.”

They also, Mr. McConnell said, “tried to hunt down the Speaker” and built a “gallows” while chatting “about murdering the Vice President.” They did this, he added, “because they’d been fed wild falsehoods by the most powerful man on earth because he was angry he lost an election. Former President Trump’s actions that preceded the riot were a disgraceful, disgraceful dereliction of duty.”

So how did Mr. McConnell justify his decision to vote not guilty? He did so by citing the Senate’s lack of jurisdiction to use what Justice Story called the “narrow tool” of impeachment on a president who was gone from office. This reportedly infuriated the House prosecutors; Congressman Raskin reckoned that Mr. McConnell had “opted to acquit Trump” on what the Washington Post paraphrased as “a constitutional technicality.”

The profundity that Mr. McConnell understands is the oxymoronic nature of a “constitutional technicality.” If something is constitutional it can’t be a technicality. Were it but a technicality, it wouldn’t be in the Constitution. Using a power one believes one doesn’t have to convict a president, or former president, would itself be an abuse of power. So we, for one, see Mr. McConnell’s forbearance as heroic.

We like the way Mr. McConnell put it when he said that the Senate is “not free to work backward from whether the accused party might personally deserve some kind of punishment.” The Republican leader went so far as to suggest that were Mr. Trump still in office, he might have voted to convict — even if “by the strict criminal standard the president’s speech probably was not incitement.”

Then Mr. McConnell issued what we predict will be a famous warning — “impeachment was never meant to be the final forum for American justice.” Impeachment and removal are, he averred, but “a specific intra-governmental safety valve.” President Trump, he marked, “is still liable” as an “ordinary citizen” for “ everything he did while he was in office.” He didn’t, Mr. McConnell added, “get away with anything, yet.”

No one can yet know whether that will prove to be a piece of prophecy or a self-serving boast. Our own instinct is that Mr. McConnell went as far as he can go without himself running off the constitutional rails. Congress, after all, is prohibited from passing bills of attainder, meaning, except for impeachment, they mayn’t act against individuals. Mr. McConnell did his duty, in our view, as he reckons the Senate did its. Now forbearance will be at enough of a premium.