Banking experts told PolitiFact that DeSantis’ claim about President Joe Biden pushing a “central bank digital currency” was dubious. Even if the system were technically feasible, current U.S. laws would not permit the kinds of monetary surveillance and control that DeSantis described, they told PolitiFact in April. The Federal Reserve is studying the possibility of creating a digital currency. But DeSantis’ remarks overstate the likelihood that such a system is possible, much less likely, to emerge in the United States -- for a variety of technical, legal and political reasons, experts told us.

-Analysis by Katie Sanders of PolitiFact

The moderators asked a question about Trump’s 2017 executive order barring immigrants from seven predominantly Muslim countries. That order led to nationwide protests and was highly divisive: 53% of Americans in a CNN/ORC poll said they opposed it at the time, while 47% said they supported it.

-Analysis by Nathaniel Rakich of 538

Crossing into the second hour of the debate, attention turned to Trump as Haley was asked if she agreed with his plan to bring back and expand his restrictions on immigration from Muslim countries.

Haley said there shouldn't be a straight ban on immigrants from Muslim countries, but rather a review of countries that have terrorist activity and represent a threat to the U.S.

"You look at what came across the southern border, what worries me the most are those that came from Iran, from Yemen, from Lebanon, those areas where they say 'death to America,'" she said. "That's where you want to be careful. It's not about a religion. It's about a fact that certain countries are dangerous and are threats to us."

DeSantis then stepped in, saying he would take it further.

"It's not just terrorism though," DeSantis said, adding: "There needs to be limits on immigration, and we should not be importing people from cultures that are hostile."

-ABC News' Alexandra Hutzler

The candidates were asked how tough they will be on high immigration at the southern border -- including the issues of unauthorized crossings and fentanyl being smuggled in.

DeSantis defended comments that he would order the military to shoot suspected drug smugglers "stone cold dead," despite critics saying that would violate the law, and he said he supports building a wall across the southern border

"The commander in chief not only has a right, you have a responsibility to fight back against these people," he said.

Haley was asked to clarify her stance on whether she would deport all unauthorized migrants. She said the U.S. has to "stop the incentive of what's bringing them over here in the first place" -- noting that President Joe Biden recently gave temporary protective status to 500,000 Venezuelans -- and also vet those who are in the country, for instance, based on their tax and employment status.

On the fentanyl overdose crisis, she turned to China, saying, "We need to end all normal trade relations with China until they stop murdering Americans with fentanyl."

Ramaswamy was asked how effective his policy to use the military to "annihilate drug labs inside Mexico" would be.

"I don't think it’s going to have to come to that if we deal with the actual demand-side problem that we also have in this country," he said. "I mean, the easy part is talking about how we’re going to use our military to secure the border. I will, and I believe that everybody else wants to do the same thing. But the harder part is dealing with the crisis of purpose and meaning, the mental health epidemic raging across the country like wildfire."

He also pointed to China as a source of fentanyl, saying, "We also have to hold them accountable with every financial lever that we have available."

-ABC News' Meredith Deliso

Addressing Trump's comments in an interview on Tuesday referring to himself as a "dictator" but only on "Day 1," Christie called the former president an "angry, bitter man who now wants to be back as president because he wants to exact retribution on anyone who has disagreed with him."

"Do I think he was kidding when he said was a dictator? All you have to do is look at the history," he said. "That's why failing to speak out against him, making excuses for him, pretending that somehow he's a victim empowers him."

Christie -- who Trump has dismissed as a failure both as a governor and candidate -- charged that the other hopefuls on stage "make it seem like his conduct is acceptable" because they said they would still support him if he was convicted of federal felonies, which Trump denies.

"Let me make it clear: His conduct is unacceptable," Christie said. "He's unfit."

Christie warned to "be careful of what you'll get."

"He will only be his own retribution. He doesn't care for the American people. It is Donald Trump first," he said, eliciting some boos from the crowd.

-ABC News' Meredith Deliso