Donald Trump got the first word, and the last word.
The first Republican presidential debate featured the real estate mogul and front-runner at the literal and figurative center of the action, with the other nine candidates trading blows with him and each other as a packed arena in Cleveland cheered them on.
Trump, who is well ahead of the rest of the Republican field five months before the first presidential nominating contest in Iowa, refused to pledge support to the eventual nominee, suggested that he would run as an independent candidate if he loses the primary race, and attacked U.S. political leaders as "stupid" and less "cunning" than their counterparts in Mexico.
"I'm, you know, talking about a lot of leverage," Trump said when asked if he could guarantee that he would support the eventual Republican nominee and not wage a potential independent campaign. "I cannot say I have to respect the person, that if it's not me, the person that wins."
"I can totally make that pledge, if I'm the nominee," Trump said.
U.S. Senator Rand Paul of Kentucky jumped in, saying, "That's what's wrong."
"He buys and sells politicians of all stripes," Paul said. "Look, he's already hedging his bets on the Clintons, OK?" The Washington Post reported Thursday that, before deciding to run, Trump called former President Bill Clinton, the husband of Democratic front-runner, Hillary Clinton.
Trump shrugged off the attack from Paul. "Well, I've given him plenty of money," Trump said of Paul. The Federal Election Commission, however, has no records of Trump contributing to Paul.
Trump is lapping the rest of the field in the polls as he demands attention of people of all political persuasions from Cleveland, the location of tonight's festivities, to California, where Republicans will be in September the next stop in their 2016 debate tour, to the Northeast, where his support is particularly strong.
On immigration, Trump doubled down on earlier comments that the U.S. is getting outsmarted by Mexican leaders, who he said are sending "criminals" over the border.
"They send the bad ones over because they don't want to pay for them, they don't want to take care them. Why should they when the stupid leaders of the United States will do it for them," Trump shouted above applause. "And that's what's happening whether you like it or not."
Paul also found himself in the center of another tussle, this time with New Jersey Governor Chris Christie over the National Security Agency and its ability to collect Americans' records.
Christie said it was "completely ridiculous" for Paul to say he wanted to collect more data on terrorists, and less on law-abiding Americans. "How are you supposed to know, man?" Christie said.
"Get a warrant!" Paul shouted, as the two talked over one another and the debate moderators struggled to keep control.
"Listen, Senator," Christie shot back. "You know, when you're sitting in a subcommittee just blowing hot air about this, you can say things like that."
Paul dug in further, saying he didn't trust the Obama administration to collect records. "I know you gave him a big hug, if you want to give him a big hug again," Paul said, referring to the embrace Christie gave President Barack Obama in the aftermath of Hurricane Sandy, during the 2012 presidential election.
Christie stared back at Paul and nodded. "The hugs that I remember are the hugs I gave to the families who lost their people on Sept. 11," Christie said.
Ohio Governor John Kasich, who received thunderous applause from his home-state crowd at Quicken Loans Arena, defended Trump, saying the New York businessman has tapped into a frustration felt by voters throughout the country.
"Donald Trump is hitting a nerve in this country,'' Kasich said. "For those who want to tune him out, they're making a mistake.''
U.S. Senator Marco Rubio of Florida hit home his key campaign message early in response to a question about his relative inexperience, one of his biggest vulnerabilities, by seeking to flip it into a strength. Throughout the debate he demonstrated a strong ability to sell Republican ideas.
"If this election is a resume competition then Hillary Clinton's going to be the next president," the first-term senator said. "This election better be about the future, not the past." He added that Clinton cannot "lecture me" about living paycheck-to-paycheck—"I was raised paycheck-to-paycheck"—or having student loans. "I owed over $100,000 just four years ago."
One stumble in an otherwise strong performance for Rubio was on abortion. Asked why someone who believes abortion is murder would support exemptions for rape and incest, Rubio disputed that premise. "I have never said that, nor have I ever advocated" exceptions to abortion rights for cases of rape and incest. But Rubio has co-sponsored anti-abortion bills that include those two exceptions (as well as when the mother's life is in danger), in 2011 and in 2013.
"Marco has sponsored pro-life legislation with and without exceptions because they enhance protections for innocent life," said Rubio spokesman Alex Conant, touting his boss's strong record with anti-abortion groups.
Rubio's fellow Floridian, former Governor Jeb Bush, said he "absolutely" understood concerns the country about dynastic politics. Bush is the son and brother of former presidents.
"I'm gonna have to earn this," he said. "Maybe the barrier—the bar's even higher for me. That's fine.''
The candidates took turns hammering Obamacare and Obama's nuclear deal with Iran. Toward the end, the Fox News moderators asked candidates what signals they had received from God. "Senator Cruz," asked Megyn Kelly, "any word from God?" The Texan proclaimed his Christian faith to be a cornerstone of his life, and said his message from God came from the Bible.
With 10 candidates vying to get their message heard, some seemed to drift out of the action for long stretches of the debate, yet Trump, who averaged more airtime than the others, was never far from the camera's lens.
The final speaker in closing arguments, the billionaire summed up his message with the bravado that has helped him shoot to the top of the polls. "Our country is in serious trouble. We don't win anymore... We can't do anything right," he said. "We have to make our country great and I'm going to do that."
—Mark Niquette contributed to this report.