Four candidates seeking the Republican presidential nomination have some momentum after focusing on issues in the third debate at Miami, Florida. The fifth — Vivek Ramaswamy — is testing Governor Jeb Bush’s warning to President Trump: “You can’t insult your way to the presidency.” 

Mr. Trump, of course, rode his Don Rickles routine to the White House in 2016. Then again, too, he had his limits, usually playing insult comic when hit first, even if critics and many supporters lamented his habit of punching down at people.