The coldest Iowa caucuses in historical past arrive Monday night time amid expectations that Republicans within the state will put former President Donald J. Trump on the march to a 3rd G.O.P. presidential nomination.

The battle for second place, hard-fought between Gov. Ron DeSantis of Florida and Nikki Haley, the previous governor of South Carolina, will anoint Mr. Trump’s closest rival forward of the New Hampshire main election and past.

The stakes for Iowans are excessive. Mr. Trump is pursuing a return to the presidency regardless of — or maybe due to — 91 felony counts from 4 felony prosecutions, a looming fraud judgment that would determine the destiny of his New York actual property empire and a pending choice on the defamation of a lady he has already been held chargeable for sexually abusing.

His opponents have implored Republican voters to transfer previous the “chaos” and controversies of the Trump period and decide a special standard-bearer to go up towards President Biden, who beat Mr. Trump in 2020. Iowans will render the primary verdict on these entreaties.

Here’s what to watch as outcomes roll in.

Historically, Iowa caucuses are squeakers, so shut that Democrats failed to produce definitive leads to the chaotic 2020 contest. Republicans falsely declared Mitt Romney the slender winner in 2012, depriving the precise victor, Rick Santorum, the momentum {that a} caucus triumph can deliver.

This time round, polling has persistently proven Mr. Trump nicely forward, a lot in order that the previous president hardly campaigned within the state. Till the ultimate weekend, he and his marketing campaign had been projecting confidence in a blowout victory, which has raised expectations when most campaigns search to decrease them.

If Mr. Trump exceeds 50 %, he’ll earn what he predicted can be “a historic landslide.” Maybe extra vital, Iowa could have signaled that even when the Republican area winnows down to Mr. Trump and one competitor, he nonetheless might have the allegiance of a majority of the get together’s main voters, at the very least within the nation’s heartland.

Mr. DeSantis formally joined the Republican presidential race in Could with robust monetary backing and speak that he would win Iowa and assist the get together flip the web page on Mr. Trump whereas nonetheless embracing his insurance policies.

However a marketing campaign equipment constructed round his tremendous PAC faltered simply as Ms. Haley was discovering her footing. She had initially targeted on New Hampshire and her house state, leaping into Iowa late.

The ultimate Iowa Ballot by The Des Moines Register, NBC Information and Mediacom, unsurprisingly, had Mr. Trump comfortably within the lead with the backing of 48 % of seemingly caucusgoers. Ms. Haley had 20 % and Mr. DeSantis 16 % — a separation on the fringe of the survey’s margin of error.

A second-place end for Ms. Haley would give her a lift forward of New Hampshire, the place she has been closing in on Mr. Trump and may benefit from Wednesday’s withdrawal of former Gov. Chris Christie of New Jersey from the presidential contest. For Mr. DeSantis, third place may spell doom forward of New Hampshire, the place he has slipped into single digits in polling averages, and South Carolina, which is a redoubt for Mr. Trump and is Ms. Haley’s house turf.

Ms. Haley’s closing argument in Iowa has been that she wouldn’t solely defeat Mr. Biden within the common election however would beat him in a convincing landslide that may ring in an period of unified conservative governance in Washington. A CBS News poll released on Sunday confirmed each Mr. Trump and Mr. DeSantis main the president narrowly, however Ms. Haley beating him by eight share factors, 53 % to 45 %.

Many Iowa Republicans are assured that Mr. Trump is a confirmed commodity who can beat Mr. Biden, regardless of the previous president’s private baggage and authorized peril. However Ms. Haley’s electability argument has been persuasive with college-educated Republican voters, 39 % of whom backed her in a New York Instances/Siena Faculty ballot launched final month.

Her activity in Iowa is to make it keep on with a big variety of Iowans with out a faculty diploma as she tries to enchantment to a wider Republican citizens that has been reworked by Mr. Trump right into a bastion of voters with out a faculty schooling. Ms. Haley, within the Instances/Siena ballot, had the assist of simply 3 % of these voters.

The Iowa caucuses have by no means been significantly democratic. The gatherings on Monday at 1,657 websites are extra like get together conferences. Locals will assemble, conduct some enterprise, hear pitches from representatives of every marketing campaign, then lastly flip in secret ballots. Caucuses might be time-consuming and public — and never significantly nicely attended.

In 2016, when Republicans held their final contested caucuses, 186,874 votes had been solid out of 615,066 registered Republicans, a turnout of about 30 %.

On Monday night time, temperatures will attain unfavorable 7 levels in a lot of the state, the place snow is blowing throughout icy roads. Mr. DeSantis has bragged of a stellar get-out-the-vote operation. Ms. Haley has the door tits of People For Prosperity Motion, a conservative activist group funded from the fortune of Charles and David Koch. Mr. Trump has a much more organized floor sport than he had in 2016, when he completed second to Senator Ted Cruz of Texas. All of that might be battling the weather.

Mr. Trump informed supporters in Indianola, Iowa, on Monday that they need to caucus even when “you’re sick as a dog.” Then he joked, “Even if you vote and then pass away, it’s worth it.”

Turnout is not going to solely have an effect on the order of the candidates’ end but in addition how actual their bragging rights are heading into the extra consultant primaries to come.

Nobody has put as a lot shoe leather-based into Iowa as Vivek Ramaswamy, the entrepreneur and more and more conspiracy-minded political newcomer who briefly noticed a spike in support in August, solely to dip again into the only digits — 8 percent in the final Iowa Poll.

There’s additionally former Gov. Asa Hutchinson of Arkansas and a Texas businessman and pastor, Ryan Binkley, each of whom got here in with 1 % within the ultimate Iowa Ballot.

Numbers like that don’t point out that any of them have enormous sway, although Mr. Trump was clearly enjoying for Mr. Ramaswamy’s voters when he attacked his erstwhile ally on Saturday.

Historically, the Iowa caucuses have winnowed out the also-rans. Former Vice President Mike Pence, Senator Tim Scott of South Carolina and Gov. Doug Burgum of North Dakota didn’t even make it to the primary casting of ballots. (Mr. Burgum endorsed Mr. Trump on the Indianola rally.)

Each Mr. Ramaswamy and Mr. Hutchinson say they are going to beat expectations.

“I believe I’m the last, best chance this country has,” Mr. Ramaswamy informed Iowans at an occasion on Friday.

However relying on their efficiency Monday, it stays to be seen whether or not they are going to drop out and decide a facet: Mr. Trump, or anybody else.