After months of flirting with the political suicide of the Republican Party in a series of juvenile, irrelevant and vulgar debates, the surviving GOP candidates went a long way last week in Miami to redeem its good name.

For two hours, Donald Trump, Sens. Ted Cruz and Marco Rubio, and Ohio Gov. John Kasich put aside the previous personal abuse and vilification and engaged in the most substantive debate of the election season. Their collective behavior hinted at possible unanticipated unity by the end of the campaign.

Rather than intensifying the focus on a stop-Trump effort, Thursday night's narrative actually fed into the celebrity businessman's reputation as a successful deal-maker. He managed during the debate to score rhetorical points on foreign trade policy, though he is widely criticized as lacking experience as well as temperament in that field.

Absent was much of Mr. Trump's familiar bombast and incivility that had made him a target of the others. Instead, he said his negotiating talents and record could benefit the U.S. in deals with China, Mexico and other trading partners.

“We're going to go out to bid in virtually every different facet of our government,” he said. “We're going to save a fortune.” He also repeated his earlier sharp criticism of President Barack Obama's nuclear deal with Iran, saying he would negotiate a much better one.

Mr. Rubio abandoned his strategy of childish and churlish personal references to Mr. Trump and instead offered serious responses on a range of issues that showed him in much improved light, though it's unlikely to do much to revive that mistake-ridden campaign.

Regarding the stop-Trump movement, 2012 GOP presidential nominee Mitt Romney has urged Republicans to vote for Mr. Rubio in his home state of Florida and for Mr. Kasich in today's Ohio primary, to leave Mr. Trump short of a majority at the July party convention. But Mr. Trump seemed to acquiesce with a moderator's suggestion that the nomination should go to the candidate with the most delegates at the end.

Mr. Cruz, currently the runner-up to Mr. Trump in the delegate count, challenged Mr. Trump on trade but with greater civility than he had shown in earlier debates, and Mr. Trump in turn did not engage him much. At one point, the celebrity mogul remarked that “so far, I can't believe how civil it's been up here.”

While Messrs. Rubio and Cruz called for raising the Social Security retirement age for future recipients, Mr. Trump said he would do “everything within my power” to maintain the current ceiling at 67. Mr. Rubio argued that “the numbers don't add up” and rejected Mr. Trump's insistence that eliminating “waste, fraud and abuse” was the answer.

As for international trade, Mr. Trump said he knew how to “take advantage” of and change rules and regulations governing it. As a businessman, he said, “I'm the one that knows how to change it. Nobody else on this dais knows how to change it like I do, believe me.”

Mr. Kasich, who has yet to win any primary but finished a close third behind Mr. Cruz in Michigan, continued his boycott of the stop-Trump effort, again selling his budget-balancing record in Congress and as Ohio governor. He has turned aside calls to quit to enable Mr. Cruz to take on Mr. Trump alone, though he has said he would withdraw if he loses the Ohio primary.

On coping with the military threat from the Islamic State, the debate brought agreement among the surviving Republican candidates that American boots on the ground are needed. They all said they would follow the counsel of American military leaders on deploying as many as 20,000 to 30,000 if so suggested by them.

But more than any specific policy position, the significance of this latest GOP debate was the conspicuous cease-fire in what had become a circular firing squad among the candidates, tarnishing the party's reputation. It remains to be seen now whether this pivot to the high road will survive throughout the remaining primaries that lead up to the July convention in Cleveland.

Jules Witcover is a syndicated columnist and former longtime writer for The Baltimore Sun. His latest book is “The American Vice Presidency: From Irrelevance to Power” (Smithsonian Books). His email is juleswitcover@comcast.net.