Haley draws fire in 4th GOP debate, Christie warns absent Trump is biggest issue

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

Haley lamented the state of economy, promising to veto any spending bill that doesn’t take federal expenditures to pre-COVID-19 levels. She slammed the Trump administration for adding $9 trillion to the federal debt.

DeSantis wouldn’t directly target Trump but chalked the the problem up to “both parties in Washington, D.C. That’s just a fact.” He pointed to student loans as an economic backbreaker for young people and touted his record on vocational education, which he said could encourage universities to become more accessible: “Don’t let anybody tell you the only way you can be successful is through a four-year, brick-and-ivy degree. That’s one way you could be, not the only way, and we’re gonna fix that problem in the United States of America.”

- ABC News’ Chris Boccia

The early back-and-forths in this debate showed an interesting dynamic between Haley-Christie and, more subtly, DeSantis-Ramaswamy. Ramaswamy has been going after Haley hard, arguably doing some of DeSantis's work for him, while Christie found himself defending Haley from Ramaswamy's attacks.

What's interesting about this, beyond the fireworks, is where Christie and Ramaswamy supporters might go as this race proceeds, as neither candidate looks to have much chance of winning the GOP nomination (to put it mildly).

Ramaswamy is closely aligned with the Trump wing of the party, which DeSantis is also part of, so some Ramaswamy supporters might look at DeSantis as a preferable option (if they don't want Trump). Meanwhile, Christie's supporters are the least Trumpy, so if he goes by the wayside, they probably would prefer Haley -- a more traditional Republican -- over DeSantis, Ramaswamy and certainly Trump.

-Analysis by Geoffrey Skelley of 538

Christie and Ramaswamy just got into a huge, personal back-and-forth while DeSantis and Haley looked on. Who might voters sympathize with more in that exchange? We can look at each candidate’s net favorability rating for a clue. Ramaswamy has a net favorability rating of +17 points among Republicans, according to 538’s average. That’s not outstanding, but it’s higher than Christie, who is at -34 points. So I’d guess that most Republicans agreed with Ramaswamy more than Christie in that exchange.

-Analysis by Nathaniel Rakich of 538