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

Trump maintains a lead of 27 percentage points over Haley, his nearest competitor in South Carolina, according to polls conducted since the first debate. Haley’s average support has grown by 9 points since the first debate, while DeSantis and Scott have fallen.

According to a September survey from Beacon Research/Shaw & Co. Research/Fox Business, 69 percent of likely South Carolina Republican primary voters say they support their first-choice candidate strongly, while 28 percent say they support them only somewhat. Among those that list Trump as their first choice, 86 percent say they support him strongly, while the second-place candidate, Haley, has only 57 percent saying the same.

In a September survey by Monmouth University/The Washington Post, South Carolina primary voters are split on whether the Republican Party should nominate a candidate who agrees with them on major issues (51 percent) or one who can beat Biden (45 percent). Among voters who say they are very or somewhat conservative, selecting a candidate who can beat Joe Biden is more important by a margin of 7 and 11 percentage points, respectively. Voters who say they are moderate or liberal prefer a candidate who agrees with them on major issues by 31 percentage points.

—Analysis by 538