After his Senate impeachment acquittal, we wrote that President Trump’s history is that he can’t stand prosperity. Well, that was fast. The President’s relentless popping off this week about the sentencing of supporter Roger Stone has hurt himself, his Justice Department, and the proper understanding of executive power. That’s a notable trifecta of self-destructive behavior even by his standards.

Mr. Trump handed another sword to his opponents when he fulminated on Twitter about the initial recommendation of a seven-to-nine…