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.

The prohibition against attacking family members is one of the few taboos left in politics and one even Mr. Trump respected — those charged with criminal behavior linked to his opponents notwithstanding. The businessman on stage Wednesday night, Vivek Ramaswamy, violated this rule in a scorched-earth performance.

Mr. Ramaswamy called the president of Ukraine, Volodymyr Zelensky, “a comedian in cargo pants.” The glib remark undercut his legitimate criticisms about corruption at Kyiv and Mr. Zelensky’s remarks this week ruling out a presidential election there in the Spring of 2024 because the country is under martial law.

Delivering memorable sound bites isn’t an automatic positive unless the goal is to get social media attention not to show presidential timber. During a debate about the Chinese Communist app TikTok, Mr. Ramaswamy wheeled on Ambassador Haley standing next to him in white — a color contrast to the mud he slung her way.

“In the last debate,” Mr. Ramaswamy said, “she made fun of me for actually joining TikTok while her own daughter was actually using the app for a long time. So, you might want to take care of your family first.”

Ms. Haley said, “Leave my daughter out of your voice.” She may have meant “mouth,” but the stumble made the moment seem more visceral and genuine. When the crowd booed, Mr. Ramaswamy said they were just “supporters propping her up.”

The cacophony, however, was louder than just her fifth of the audience. When Ms. Haley muttered, “You’re just scum,” Mr. Ramaswamy didn’t respond. It gave the impression that he was so intent on hearing his own quips that he wasn’t listening to anyone else.

Mr. Ramaswamy targeted the other candidates, too. He hit two birds with one stone by criticizing Ms. Haley’s “three-inch heels” — “five-inch,” she corrected — and those Governor DeSantis has been alleged to wear.

Even a moderator of NBC News, Lester Holt, didn’t escape unscathed. Avoiding a question, Mr. Ramaswamy demanded that the journalist answer for his network’s false Russia collusion reporting and suggested “Tucker Carlson, Joe Rogan and Elon Musk,” would have been more appropriate.

The strategy of Republicans, with a voter-registration disadvantage of 11.6 million against Democrats, speaking only to outlets favored by their hardcore base is flawed. Only a single GOP candidate has captured the popular vote since 1988. Victory is impossible without reaching crossover voters.

“Preaching to the choir,” as I wrote in the Sun following Republican losses in last year’s midterms, “is a good strategy to land contributions, book deals, and a Fox News Channel consulting gig, but not to win elections.”

Being young and a good speaker has brought Mr. Ramaswamy press attention and all the laurels that go with it. It also propelled him onto the stage with three governors and a senator who showed him respect that he would have been wise to offer in return.

Senator Scott of South Carolina showed how to best deal with moderators by saying he disagreed with the premise of a question posed by another NBC News journalist, Kristen Welker. When it was Ms. Haley’s turn, she made a point of agreeing with his point.

Mr. Trump may like Mr. Ramaswamy’s approach. The former president — a smaller elephant in the room than he was in the first debates — has said he may treat the events as an audition for vice president.

Like Mr. Scott, Ms. Haley, and Governor Christie of New Jersey, Mr. DeSantis hewed to issues, which may be less attractive to Mr. Trump. The Florida governor, like Mr. Christie and Ms. Haley, has committed Mr. Trump’s mortal sin of “disloyalty.” Plus, both men live in Florida, which presents a complication owing to the Constitution restrictions on the Electoral College:

“The electors,” the Constitution ordains, “shall meet in their respective states, and vote by ballot for two persons, of whom one at least shall not be an inhabitant of the same state with themselves.” It would prevent electors from Florida voting for both Messrs. Trump and DeSantis.

Mr. Christie knows he’s not on Mr. Trump’s short list to be vice president as he was in 2016, but he admonished Mr. DeSantis, Ms. Haley, and Mr. Ramaswamy for infighting. “These three in the middle,” he said, “think they’re the enemy. I know China is the enemy.”

The sparing of Mr. Scott was telling. Mr. Trump can be expected to be the dominant personality on the GOP ticket. The senator — a quiet, serious candidate with a strong Christian faith — could provide the same balance that Vice President Pence brought in 2016.

All five candidates backed Israel’s war with Hamas while promising to get tough on Beijing and on America’s border, citing the influx of fentanyl. Inflation and tilting abortion law toward the unborn faded, although when the issue was raised, the candidates connected with empathy.

The candidates detailed Iran’s role in sponsoring terrorism. Mr. Scott repeated his charge “there’s blood dripping from the hands of” Presidents Biden and Obama for sending money to Tehran. On policy, it was the night’s breakout moment.

Except for Mr. Ramaswamy, all the candidates supported a form of funding resistance to Russia while urging the provision of a stronger Navy to protect Free China. Mr. Christie called nuclear submarines “the greatest deterrence to Chinese aggression.” 

Without Mr. Trump, ratings for the debate were no doubt low, as Mr. Trump is like to mention. That’s too bad, because four candidates with a mastery of issues and a vision for the future made solid cases for being commander-in-chief.

The fifth, Mr. Ramaswamy, may see a bump in the polls and an influx of campaign donations, but it’s hard to see a path to the nomination. The Republican Party is on track to choose the Rickles they know for the top of the ticket — and this time around, Mr. Scott may be the perfect straight man for the act.