Among those who have long argued for the need to rethink presidents’ “sole authority” powers are former Defense Secretary William J. Perry, considered the dean of American nuclear strategists, who has cited the fragility of a nuclear-weapons control chain and the fear that it can be subject to errors of judgment or failure to ask the right questions under the pressure of a warning of an incoming attack.

Mr. Trump’s critics have long questioned whether his unpredictable statements and contradictions pose a nuclear danger. But the concerns raised last week were somewhat different: whether a president taking mood-altering drugs could determine whether a nuclear alert was a false alarm.

That question is a new one. The military’s Strategic Command often conducts drills that simulate actual but inconclusive evidence that the United States may be under nuclear attack. Such simulations drive home the reality that even a president asking all the right questions could make a mistake. But they rarely simulate what would happen if the president’s judgment was impaired.