Christie criticized the idea that the president could cozy up to Vladimir Putin, noting that all recent presidents have failed to engage Putin by not being tough enough. He then hit Trump for having said that Putin was "brilliant and a great leader." As the night has worn on, Christie continues to be really the only candidate who is bothering to attack the guy who is 40 or more points ahead of every other candidate in national GOP primary polls.

— Analysis by Geoffrey Skelley of 538

Ilia Calderón is asking about sending U.S. troops to Mexico. In a late August/early September survey by Morning Consult, 41 percent of Republicans said they thought that sending U.S. troops to fight cartels in Mexico would be “very effective” at limiting the supply of illegal drugs in the United States. Other strategies had more support among Republicans, such as sending more resources to the U.S.-Mexico border (54 percent), empowering U.S. law enforcement to combat opioids (45 percent), and punishing drug violators in the United States (43 percent).
—Analysis by 538

Haley going after Ramaswamy was a recurring theme in the first debate. They were the standout candidates in our polling last time and there was a lot of speculation about Ramaswamy moving up in the polls — perhaps even surpassing DeSantis. But since August, Ramaswamy has actually lost support, to the point where Haley passed him in our polling average today. It makes sense that they're trading blows again; this seems to be a successful strategy for Haley, and Ramaswamy can't help but take the bait.
-Analysis by G. Elliott Morris of 538

The candidates are discussing support for Ukraine. About half (49 percent) of Republicans and Republican-leaning independents say that vital U.S. interests are not really at stake in the war in Ukraine, according to an August Echelon Insights survey. Thirty-seven percent disagree, saying that if Russia wins, vital U.S. interests and values are threatened. Fourteen percent are unsure.
—Analysis by 538

In anticipation of tonight’s debate, we again partnered with The Washington Post and Ipsos to ask likely Republican primary voters what they think about tonight’s debate participants and the candidate field in general.

The 5,002 likely Republican primary voters we polled using Ipsos’s KnowledgePanel expect DeSantis and Ramaswamy to perform best, out of the seven-candidate field. According to a five-point scale that we calculated using respondents’ answers (with 1 being “terrible” and 5 being “excellent”), likely voters expected both DeSantis and Ramaswamy to perform “very good” (3.44 and 3.43 out of 5, respectively). They thought Haley would perform third-best (3.40 out of 5) and Scott fourth (3.20 out of 5). All of this is fairly in line with their pre-debate expectations in August.

When it comes to which candidates respondents are interested in, Haley saw the biggest bump since our poll before last month’s debate — 31 percent are now considering voting for Haley, up from 25 percent. Although she now has the third-most prospective support, she’s still got a long way to go compared to Trump (66 percent) and DeSantis (49 percent). About 1 in 4 likely Republican primary voters are also considering voting for Ramaswamy and Pence.

We’ll be watching to see how the candidates fare tonight, and if debate watchers’ opinions on who they’re considering voting for will change after tonight’s performances.

—Analysis by Holly Fuong of 538