WASHINGTON — Republican presidential front-runner Donald Trump heads into the Iowa caucuses Monday with a commanding 48% support in a closely watched poll that showed Nikki Haley moving into second place with 20%.

The results of the NBC News/Des Moines Register poll suggest further trouble for Ron DeSantis, who dropped to third place with 16%, two days before the nation’s first Republican nominating contest. The Florida governor is banking on a strong showing in Iowa to bolster his challenge to the former president.

Severe winter weather descended on Iowa while the poll was still being conducted, and subzero temperatures forecast for Monday night risk chilling turnout among Iowa’s famously late-deciding caucusgoers when they gather in 1,657 precincts.

The poll signals a slight softening from the 51% support that Trump notched in the last NBC/Des Moines Register survey in December. Still, Trump’s lead is just below the majority threshold that would signal a blowout victory in the kick-off to the presidential nominating contest.

The Des Moines Register poll is considered the gold standard in Iowa polling and helps to set the stage going into an event where meeting or exceeding expectations can be almost as important as the result itself.

Pollster Ann Selzer said the lack of enthusiasm among Haley’s supporters was “on the edge of jaw-dropping.”

About half of Trump’s supporters said they were extremely enthusiastic about caucusing for the former president. Only 9% of Haley’s supporter’s said the same.

Ohio businessman Vivek Ramaswamy was in fourth place in Iowa with 8%. The poll of 705 likely Republican caucusgoers was conducted Jan. 7-12, and it has an overall margin of error of plus-or-minus 3.7 percentage points.

The poll took place during a tumultuous final week of campaigning that culminated in a winter storm that brought much of the state to a standstill.

Haley and DeSantis squared off one-on-one in an insult-driven televised debate Wednesday, then battled the frigid Iowa weather in a final pre-caucus blitz.

Trump, who arrived in Iowa late Saturday, spent much of the last week in courtrooms in Washington and New York, defending himself against allegations that he tried to illegally retain power after losing the 2020 election and that he committed fraud by inflating the value of his real estate holdings.

Iowa political wisdom holds that there are “three tickets out of Iowa.” But this year, even a narrow Trump victory would put pressure on the third-place finisher to drop out to allow the anti-Trump vote to consolidate around a single alternative in the New Hampshire primary on Jan. 23. Haley now trails the former president by just 14 points in the RealClearPolitics average of New Hampshire polls.