President Joe Biden was mentioned and attacked by candidates at the debate much more than former president and current candidate Trump was, a rough real-time ABC News count shows -- with Biden mentioned at least 10 more times than Trump.

Ramaswamy seemingly faced the most attacks from other candidates at the debate, followed by DeSantis and Pence.

Burgum and Hutchinson faced effectively no direct attacks from other candidates.

-ABC News' Oren Oppenheim

Let me put my wannabe political scientist's hat on for a second. We heard a lot tonight about what ails America: crime, climate change, inflation, bureaucracy (some issues are more persuasive than others). And the candidates presented various visions for combating those issues — again, some more persuasive than others! But as is always the case, a lot of what we see in these debates is just theater. There are serious doubts that these contests can really accomplish most of what these candidates are trying to sell — indeed, some of the problems may come down to the structure of these primaries in general. Next time, if the candidates are trying to run for president, they should really just stick to talking about their electability.
-Analysis by G Elliott Morris of FiveThirtyEight

Perhaps unsurprisingly, the pugnacious Christie repeatedly mixed it up with other candidates tonight. He was critical of Trump, calling the front-runner's behavior "unbecoming" and making him unfit to be president. Christie has a track record of strong debates, having shown in 2016 how he can throw a verbal punch, including his famous takedown of Marco Rubio just ahead of the New Hampshire primary that year. But Christie's criticism of Trump and his high unfavorable ratings among Republicans make his performance unlikely to cause a Christie boomlet in this race.

For Scott, tonight was an opportunity to capitalize on his potential as a candidate who is well-liked by Republicans familiar with him but who is not that well-known. And he largely tried to stay above the fray on most issues, which in theory made sense if he wanted to look like a consensus-style candidate who most Republicans could like. However, that also led to him getting less airtime, as the candidates who engaged each other and freely interrupted were more likely to be on camera. This debate doesn't hurt Scott, but I'm skeptical it helped him much.

-Analysis by Geoffrey Skelley of FiveThirtyEight

Nikki Haley has been in the race for longer than anyone else on the stage but hasn't had a breakout moment yet. She was clearly aiming to change that tonight, and she did have one of the most memorable back-and-forths of the night when she took Ramaswamy to task over his lack of foreign policy experience. She came out swinging early not just against Biden but against Republicans in Congress, and she was one of just a handful of contenders to make an electability argument against Trump by pointing out his low favorability ratings. But for a candidate who is polling at 3.4 percent nationwide, it's not obvious that was enough.

Burgum's presence was a victory in and of itself for the governor, given his injury today. But he got scant talking time, and his most interesting answer, when he came out definitively against a national abortion ban, isn't likely to earn him many new fans in the GOP.

But here's what I really think. The next debate is not for another month, but tomorrow, Donald Trump will surrender to the authorities in Atlanta. His mugshot will ricochet across the internet and land on the front page of every major newspaper in the country. At that point, will people be talking about tonight's debate? Or will they be back to talking about Trump? I'd put my money on the latter, and that's not good news for anyone on stage tonight.
-Analysis by Jacob Rubashkin, Inside Elections

Recent election cycles have shown how debates can substantially alter a candidate’s trajectory. The debates won’t always do this, of course, and early primary polls remain relatively predictive of who will end up winning a party’s nomination. However, a candidate can earn a real polling bounce from a debate — or fall into a valley.

Primary polls are inherently more volatile than general election polls. In a general election, most voters already lean toward one party, so only a small part of the electorate is likely to shift its views over the course of a campaign. But in a primary, voters in one party may be open to multiple candidates because most contenders will share similar views on a number of issues. As a result, exposure to an unfamiliar candidate could prompt voters to begin considering that contender, while a strong or weak performance by a candidate they do know could make them look elsewhere.

For example, early in the 2012 cycle, Texas Gov. Rick Perry appeared to be now-Sen. Mitt Romney’s most serious opponent for the Republican nomination. But in a September 2011 debate, Perry defended a Texas policy that gave undocumented immigrants access to in-state college tuition. The backlash from the GOP base came swiftly, as Perry fell out of contention in the polls, well before a later debate in which he — oops — forgot the name of the third of three federal agencies that he aimed to dismantle as president. Four years later, former tech executive Carly Fiorina had very little support early in the 2016 Republican race, but in August 2015 she stood out in an “undercard” debate. Her polling numbers improved and she made the main stage in subsequent debates, giving her a platform that eventually led Texas Sen. Ted Cruz to make her his vice presidential pick in a last-ditch attempt to rally support against Trump in the 2016 primary.

-Analysis by Geoffrey Skelley of FiveThirtyEight