Donald J. Trump has the backing of 48 percent of likely caucusgoers ahead of Monday’s election, a commanding lead for the former president, according to the Iowa Poll by The Des Moines Register, NBC News and Mediacom.
Nikki Haley is narrowly leading the battle for second place over Gov. Ron DeSantis of Florida, 20 percent to 16 percent, according to the survey, which was released on Saturday evening.
The poll shows Ms. Haley, the former United Nations ambassador, improving compared with December and Mr. Trump slipping — but only marginally. He enjoys a 28-point lead, compared with a 32-point advantage last month.
The survey has almost nothing but good news for the former president. He leads with every demographic group tested, performing most strongly among those without a college degree, those earning less than $50,000 and men who did not graduate from college. He pulled in the support of roughly three in five voters in those three categories.
His supporters were also more enthusiastic about voting than those of his rivals, and Ms. Haley’s enthusiasm levels were markedly below his — and even below Mr. DeSantis’s.
And Mr. Trump is ahead by so much that his support is greater than what Ms. Haley and Mr. DeSantis are garnering — combined.
More than two-thirds of voters said they had made up their minds, while only 7 percent said they did not yet have a first-choice candidate on the cusp of the caucuses. One in four likely caucusgoers said they could still be persuaded to pick a new candidate.
The survey, which has taken on an almost mythic status in some political circles, immediately forms the new base line of expectations for the caucuses on Monday. All three leading candidates have been fighting not just to win the most votes in recent days but also to dampen how well they are expected to perform in order to claim a stronger-than-expected showing.
No other candidate was in double digits, with Vivek Ramaswamy, a businessman who has aligned himself with Mr. Trump and has campaigned heavily in Iowa, at 8 percent.
The caucuses are not limited to Republicans — both independent voters and Democrats can vote in the election, if they re-register as Republicans on caucus night.
One of the survey’s more striking findings is that roughly half of Ms. Haley’s support is coming from independents (39 percent) and Democrats (11 percent).
Ms. Haley’s strongest demographic groups are no surprise — those who live in suburbs and white women with college degrees — but even among those constituencies she does not lead Mr. Trump.
Historically, one of the most important groups in Iowa Republican caucuses are evangelical voters, and Mr. Trump leads widely among those voters, with 51 percent. Mr. DeSantis is a distant second with 22 percent, but that is actually lower than his support level among that demographic in the December survey. Ms. Haley is pulling only 12 percent among evangelical voters.
The poll — conducted by J. Ann Selzer from Jan. 7 to 12, with a margin of error of 3.7 percentage points — comes during an unusual cold snap even for Iowa.
The weather has made turnout predictions on Monday especially volatile. The Trump, DeSantis and Haley campaigns have been studying the impact of the storm for any potential advantage, with unaligned political strategists calling the cold — with subzero highs for the day — an unusual test of both natural enthusiasm and organizational might in the race’s final days.
“You have the worst weather, I guess, in recorded history but maybe that’s good, because our people are more committed than anybody else,” Mr. Trump said in a video announcing that he was canceling some of his weekend’s events.
The poll does show an enthusiasm edge for Mr. Trump. He has the largest share of enthusiastic supporters, with 49 percent saying they are extremely enthusiastic and 39 percent very enthusiastic.
In comparison, Ms. Haley’s backers were far less excited. Only 9 percent said they were extremely enthusiastic to support her, and 30 percent very enthusiastic.
Ms. Selzer told The Des Moines Register that the low levels of enthusiasm for Ms. Haley “are on the edge of jaw-dropping.”
There is one strong result in the poll for Mr. DeSantis on a caucus night expected to set records for its cold temperatures: His supporters were the most likely to say they will definitely caucus, with 62 percent saying so, slightly above the numbers for Mr. Trump or Ms. Haley.
In the previous Iowa Poll, in December, Mr. Trump was the first choice of a 51 percent majority of likely caucusgoers, and leading among every demographic group. He was dominating by an even wider margin among first-time caucusgoers, with 63 percent support.
Mr. Trump had grown from 42 percent in August, 43 percent in October and 51 percent in December, and dipped for the first time to 48 percent in the new poll.
Mr. DeSantis had previously stayed relatively steady: 19 percent in August, 16 percent in October and then 19 percent again in December. He dropped back to 16 percent in this latest survey.
Ms. Haley began far behind, with 6 percent in August, but she is the only candidate who has not dropped since. She rose to 16 percent in October, stayed at 16 percent in December and hit a new high of 20 percent in this survey.