In his first annual message to Congress, John Quincy Adams, among the most experienced and intellectually formidable presidents, warned leaders against giving the impression that “we are palsied by the will of our constituents.” In this regard, if in no other, the 45th president resembles the sixth.

Donald Trump’s “Oh, never mind” presidency was produced by voters stung by the contempt they detected directed toward them by the upper crust. Their insurrection has been rewarded by Trump’s swift shedding of campaign commitments, a repudiation so comprehensive and cavalier that he d...