WASHINGTON — Over the course of just 17 hours this weekend, President Trump assailed John McCain, Chuck Schumer, Stephen Curry, the National Football League, Roger Goodell, Iran and Kim Jong-un — the “Little Rocket Man.” And that was on his day off.

While football players knelt, locked arms or stayed in their locker rooms during the national anthem in protest on Sunday, any notion that Mr. Trump may soften his edge, even under the discipline of a new chief of staff, seemed fanciful. While he has restrained himself for brief stretches, his penchant for punching eventually reasserts itself.

Never in modern times has an occupant of the Oval Office seemed to reject so thoroughly the nostrum that a president’s duty is to bring the country together. Relentlessly pugnacious, energized by a fight, unwilling to let any slight go unanswered, Mr. Trump has made himself America’s apostle of anger, its deacon of divisiveness.

His denunciation of what he called unpatriotic sports stars protesting racial injustice by not standing for the national anthem clearly cheered supporters at a rally in Huntsville, Ala., on Friday. For his admirers, his attacks on entitled elites can be bracing and invigorating, finally giving voice to grievances they consider long ignored. Whether by design or not, they also distract from other matters, in this case another looming legislative debacle as his health care bill faces defeat in the Senate.