Still, the Senate confirmed him, and he was clear that he would not recuse himself on these grounds. And in reaching a prosecutorial judgment on obstruction, Mr. Barr consulted Mr. Rosenstein, who concurred in the decision to decline prosecution; he also claims to have engaged the Office of Legal Counsel.

These process norms fared well. But the Mueller report marked a low point for more substantive norms of presidential conduct. It shows that a demagogic president like Donald Trump can devalue or even depart radically from key norms, just short of committing chargeable crimes, so long as he operates mostly and brazenly in full public view. For a demagogue, shamelessness is its own reward.

Such a president can have openly, actively encouraged and welcomed foreign government support for his political campaigns, and his campaign can reinforce the point in direct communications with that government’s representatives. The Barr summary reveals that the special counsel uncovered not just a couple but “multiple offers” of support from the Russians, and yet neither Mr. Trump nor his campaign reported them to counterintelligence or law enforcement authorities. Mr. Trump went further still — while in office, he dictated a statement for his son and campaign aide, Donald Trump Jr., that falsely represented the purposes of the June 2016 Trump Tower meeting between senior campaign representatives and a Kremlin-connected representative (and others) offering assistance in the 2016 election.

Mr. Mueller proceeded cautiously on this and other evidence. Federal campaign finance laws prohibit soliciting and receiving support from foreign nationals or “substantially assisting” them in their efforts to influence an American election, but Mr. Mueller concluded that the rules as applied to the facts did not support a criminal prosecution. This was a conservative judgment — but it underscores again the urgent work norms must do if the law is inadequate to the task.

Similarly, the letter notes that much of the president’s obstructive behavior during the investigation was in “public view.” This was apparently a significant consideration in the decision by Mr. Barr and Mr. Rosenstein not to prosecute (along with the determination that there was no underlying “collusion” legal offense). Here, once again, the president who is a demagogue — who is fully prepared to flout well-established, vitally important expectations about how American presidents faithfully execute the laws — can safely bring self-interested, self-protective pressure on the Department of Justice and undermine its public standing and authority.