Thursday night’s Republican debate in Miami saw a dramatic shift in tone from recent GOP clashes, which had been marked by rancorous exchanges and name-calling. 
 
 The change surprised even front-runner Donald Trump Donald TrumpOvernight Defense: Speculation grows over Trump national security picks Trump wants son-in-law to sit in on daily briefings: report Herman Cain: 'Steve Bannon is not a white supremacist’ MORE, who said at one point, “I cannot believe how civil it’s been up here.” 
 
 But who gained and who lost as crucial primaries loom in Florida, Ohio and several other states on Tuesday? 
 
 WINNERS 
 
 Businessman Donald Trump 
 
 One of the ironclad rules of political campaigns is that a front-runner gains from a debate that produces no game-changing moments. 
 
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 By that standard, Trump had by far the best night on Thursday. His rivals highlighted their differences with him, but there was little personal enmity. Trump maintained a calmer demeanor throughout and was never knocked off his stride. 
 
 Trump leads in Florida, Tuesday’s biggest prize, by more than 15 points according to the RealClearPolitics (RCP) polling average, so the relative lack of debate drama will be just fine with him. 
 
 The businessman’s performance was also characterized by repeated calls for the GOP to unify around him and to “embrace” his capacity to bring new voters to the party. Trump has for some time been focusing attention on what he sees as his electability in the fall, and this was the most pronounced example yet. 
 
 In an interview with CNN’s Chris Cuomo moments after the debate ended, Trump declared that the evening had been “elegant” and said, “We needed this kind of a debate.” 
 
 Those aren’t the words of a man who was unhappy with anything that happened during the previous two hours. 
 
 The Republican Party 
 
 There had been widespread consternation within the GOP about the nature of the most recent two debates, one of which featured Trump responding to a Rubio campaign-trail innuendo about his genitalia. 
 
 The party establishment may not yet be reconciled to the prospect of Nominee Trump, but there will at least be a collective sigh of relief about the more measured exchanges on Thursday night in Miami. 
 
 Policy wonks will also have derived some satisfaction from the evening, which featured substantive discussions about a wide range of issues, foreign and domestic, from Social Security and veterans’ affairs to trade agreements and relations with Cuba. 
 
 Sen. Marco Rubio Marco RubioRubio: 'I have no reaction’ to Bannon hire NFL players visit DC for dialogue on race Insurers brace for ObamaCare upheaval MORE (Fla.) 
 
 Rubio entered this debate on the ropes. He suffered a dismal series of election results in Tuesday’s contests, and there is no real evidence that he is clawing his way back into contention in his home state. 
 
 Perhaps wisely, he didn’t try to knock out Trump, or anyone else, with a single blow on Thursday night. Instead, he delivered a solid performance that will have reminded his supporters why they believe in him. 
 
 He also likely helped himself in the Sunshine State on a couple of issues. 
 
 His critique of President Obama’s decision to reopen diplomatic relations with Cuba was powerful, and he walked a fine line effectively on Social Security reform in a state that has more than 3.1 million retirees receiving benefits, as co-moderator Jake Tapper noted. While Rubio proposed gradually raising the retirement age, he also noted that, “I’m against any changes to Social Security that are bad for my mother.” 
 
 Make no mistake, Rubio’s chances of the nomination are exceedingly slim at this point — and they could expire completely if he loses the Florida primary. But he acquitted himself well on Thursday night nonetheless. 
 
 MIXED 
 
 Sen. Ted Cruz Ted CruzCruz, Marla Maples, Tommy Hilfiger all seen at Trump Tower Supreme Court now in Trump’s hands The conservative case against filibuster reform MORE (Texas) 
 
 Cruz can take satisfaction from the fact that he is clearly the biggest threat to Trump’s quest for the nomination. His debate performance Thursday was proficient, as it almost always is, but he delivered no moments spectacular enough to derail the Trump train. 
 
 The Texas senator continues to assail Trump over his conservative bona fides. 
 
 On Thursday, he said that it was a “matter of public record” that the business mogul had supported Democratic nominee John Kerry John KerryUS agrees to take refugees detained by Australia White House hails new Colombia peace agreement Kerry sidesteps Trump talk in Antarctica MORE over incumbent Republican President George W. Bush in the 2004 election and had given money to Hillary Clinton Hillary Rodham ClintonGOP rushes to embrace Trump Mark Mellman: What happened to the polls? DNC charter requires chairman be full time MORE for her 2008 presidential campaign. He also knocked Trump for, in Cruz’s view, his insufficient support for Israel. 
 
 Still, this was a more subdued Cruz than on previous occasions. He may have calculated that going into full-on attack mode would hurt rather than help him or that he should bide his time until other candidates drop out and leave him in a one-on-one battle with Trump. 
 
 But time is running perilously short for anyone hoping to beat Trump. Cruz at one point highlighted that he was only about 100 delegates behind the front-runner and that he had beaten him in a number of states. 
 
 Trump shot back immediately: “He’s always saying, ‘I’m the only one that beat Donald in six contests, and I beat him.’ But I beat him in 13 contests. He never mentions that.” 
 
 All Cruz could do was smile. 
 
 Ohio Gov. John Kasich 
 
 Kasich, a more uneven debater than Cruz, had a respectable night. But a highlight reel for the Ohio governor would be very short indeed. He was competent but not memorable. 
 
 Kasich also suffered from an unusual dynamic. In the most recent debates, he had been able to distinguish himself by his positivity amid rampant mud-slinging. With his rivals adopting a more dignified tone on Thursday, Kasich stood out less starkly. 
 
 LOSERS 
 
 Democrats and fans of recent GOP debates 
 
 Democrats had reacted with undisguised glee to previous Republican debates, which they believed damaged the party’s brand and curbed its capacity to reach out to voters in the center ground. There was much less for them to latch onto on Thursday. 
 
 They were not left entirely without ammunition. Trump’s description of the 1989 pro-democracy Tiananmen Square uprising in China as a “riot” will surely find its way into an attack ad if he does become the GOP nominee. 
 
 When Rubio suggested concerns about climate change were overstated, Rep. Debbie Wasserman Schultz (Fla.), chairwoman of the Democratic National Committee, immediately excoriated him on Twitter. 
 
 Still, those were slim pickings compared to sound bites about the size of parts of Trump’s anatomy or clashes that featured his repeated mocking of his two main rivals as “Little Marco” and “Lying Ted.” 
 
 Of course, there are other viewers — not all of them Democrats — who have loved the WWE style of those recent debates. Thursday night, by those standards, just didn’t pack the same punch. ||||| At the CNN debate in Miami, GOP candidates sparred over immigration, social security, how to talk about Muslims and more. Here are the key moments. (Sarah Parnass/The Washington Post) 
 
 At the CNN debate in Miami, GOP candidates sparred over immigration, social security, how to talk about Muslims and more. Here are the key moments. (Sarah Parnass/The Washington Post) 
 
 Through 12 Republican debates, there has been one consistent dynamic: Donald Trump has held center stage, literally and figuratively. He is the alpha politician who has fended off multiple opponents with cutting insults, timely interruptions and only an occasional exploration of the substance of policy. 
 
 Trump shared a debate stage Thursday night with his three remaining rivals, Sen. Ted Cruz of Texas, Ohio Gov. John Kasich and Sen. Marco Rubio of Florida, and he found a different way to control the evening: by deflection and adaptability. 
 
 Ahead in the race for the nomination, he adopted a more restrained and subdued demeanor, even passing up opportunities to strike back when his opponents tried to engage him. It was a strategy common to front-runners — play not to lose, avoid mistakes or eruptions, and force the opposition to change the dynamic. 
 
 For much of the evening, the four candidates carried on a generally civil discussion on the issues. They avoided the kinds of clashes that had created a downward spiral in their dialogue over the three previous debates. 
 
 Thursday’s encounter, in particular, seemed a direct reaction to the universal criticism of their debate a week ago, a forum that took the GOP campaign into the gutter. But in the more subdued environment, Trump was challenged anew to move beyond generalities, and he still struggled to explain where he really stands on a range of issues, from education and trade policy to Social Security and the federal budget deficit to dealing with the Islamic State and Iran. 
 
 1 of 18 Full Screen Autoplay Close Skip Ad × The Republican presidential candidates faced off during the CNN debate in Miami View Photos The four remaining candidates debated in Miami, five days before the winner-take-all GOP primary in Florida on March 15. Caption The four remaining candidates debated in Miami, five days before the winner-take-all GOP primary in Florida on March 15. March 10, 2016 Republican presidential candidate Donald Trump, left, shakes hands with rival Ted Cruz as they arrive onstage for the CNN debate at the University of Miami. Carlo Allegri/Reuters Buy Photo Wait 1 second to continue. 
 
 That Trump has certain skills as a candidate is without question. He can dominate a debate or a news cycle with relative ease. His ability to keep opponents at bay and off balance has been stellar. But there is much more to being president than that, which is why there are so many doubts about him among the electorate at large. What the debates have shown is that Trump’s lack of depth on issues continues to be a key part of the story of his quest for the presidency. 
 
 Trump arrived at Thursday’s debate at the University of Miami nearing what could be a key turning point in the Republican campaign. By Tuesday night, after a round of primaries in big states, he either will be seen in full command of the nomination process — virtually unstoppable — or facing competition that could carry on all the way to the floor of the GOP convention in Cleveland in July with no certain outcome. 
 
 The New York billionaire has gotten to this moment through the systematic destruction of his opponents. He is a ruthless attacker and a pitiless counterpuncher. He reads people and goes for the jugular. He delights in putting down his opponents and shows no mercy as he does so. 
 
 Three candidates in particular have threatened him, and he has lashed at each. He unnerved Jeb Bush by declaring the former Florida governor the “low energy” candidate. When he called Rubio “Little Marco,” the tag seemed almost instantly to diminish the politician in whom so many establishment Republicans had invested their hopes. 
 
 Playing Trump’s game has proved foolhardy. Bush vacillated in his response to Trump’s insults until his candidacy had little oxygen left. Rubio finally responded when his candidacy was in deep trouble. Goaded into a direct battle, Rubio went down to Trump’s level of insults. He said this week he now regrets what he did. Rubio’s faint hopes of continuing depend on winning his home state on Tuesday, but he trails in the polls. 
 
 “Lyin’ Ted” is Trump’s belittling shorthand for Cruz. The two seemed to share a bromance for months, until it was clear to each that the other represented a mortal threat to his hopes of becoming the nominee. Cruz, however, has shown more resilience in the face of Trump’s attacks than Bush or Rubio, at least so far. He is second in states and delegates won. 
 
 Kasich has avoided attacking Trump and, in turn, has avoided being attacked. But can anyone beat Trump by trying to ignore him, as Kasich has done? Not likely. If the governor beats Trump in Ohio on Tuesday, he’s likely to find himself under attack, and a new chapter in their relationship will begin to unfold. 
 
 But if Trump’s rivals have failed to knock him down by playing his game of insult and attack, they also have struggled to capitalize on those limitations, which says something about both them and Trump. If the New York businessman ultimately is denied the nomination — or eventually the presidency, should he become the nominee — it could be as much his fault as anything else. After nine months as a politician, there is still a question as to how much he has grown as a candidate. 
 
 On Thursday, he was pressed to explain his opposition to the education policy known as Common Core. “Education through Washington, D.C.,” he replied. When CNN’s Jake Tapper pointed out that Common Core was developed by governors and the states and that the standards are voluntarily adopted by states and localities, Trump said, “It has been taken over by Washington.” 
 
 When Kasich was asked about Common Core, he offered a deeper description of what he has done in Ohio on a range of education issues. Cruz, who opposes Common Core, outlined a series of proposals to expand charter schools, home schools, school vouchers and the like. “It’s easy to talk about the problem, but you have to understand the solutions.” 
 
 CNN’s Dana Bash pressed Trump to explain how he would preserve the financial viability of Social Security without making adjustments in the retirement age, benefits or anything else. Trump said he would attack waste, fraud and abuse. When Bash told him that estimates suggest that would accomplish very little, Trump shifted his focus to the cost of U.S. military obligations overseas. 
 
 This time it was Rubio who suggested the front-runner has limited knowledge of the problems he wants to solve. “The numbers don’t add up,” he said of Trump’s proposal. “The bottom line is, we can’t just continue to tiptoe around this and throw out things like I’m going to get at fraud and abuse.” 
 
 Trump responded by claiming that changes in the government’s bidding process would reap major dividends. “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.” 
 
 So it went through much of the debate — the most substantive discussion of any of the debates on an evening when Trump’s rivals sought to undermine him on the substance rather than theatrics. 
 
 On foreign policy, Trump was told that he didn’t understand that his Middle East policies were anti-Israel, even though he claimed that he was more pro-Israel than anyone else on the stage. He was accused of wanting to continue policies closer to those of President Obama and former secretary of state Hillary Clinton rather than change direction, as many Republicans are demanding. 
 
 Cruz delivered a cutting description of Trump’s foreign policy philosophy as, “China bad, Muslims bad.” 
 
 It was an entirely different approach by Trump’s opponents, and response by the New York billionaire. The criticisms produced few fireworks and probably muted headlines on Web pages all over the country. 
 
 Trump continued on a plane of generalities more than specifics. That has worked for him through the course of the nomination battle, but it leaves unanswered exactly what he would do as president.
– The Republican presidential debate Thursday in Florida was—as Harry Enten at FiveThirtyEight puts it—a "180-degree turn from the last debate" when Donald Trump famously reassured America on the size of his penis. The opening questions of the debate hit topics including trade, jobs, education, and social security. FiveThirtyEight notes it was both a "serious tone" and a "pretty stark change in tone" from the last debate, with none of the candidates particularly disagreeing with one another. "I can't believe how civil it's been up here," Trump added at the end of one of his responses. Trump even used his opening statement to call for Republican unity, as long as that's unity behind him, Politico reports. "I think frankly the Republican establishment, or whatever you want to call it, should embrace what is happening,” Trump said. It's unclear how the less combative, less crude debate tenor will play out for the candidates. "The civility may be a good thing for voters, but it's really boring television," Clare Malone at FiveThirtyEight writes.