Treacherous travel conditions may impact turnout, US Correspondent Dan Rivers reports
The interstate highway 80 across Iowa is treacherous.
Littered with dozens of jack-knifed lorries and abandoned cars, it is a reminder of how the weather will affect the Iowa caucuses - a series of meetings where party members choose their preferred presidential nominee.
The temperature has been well below zero.
That’s zero Fahrenheit. In centigrade that is -17.
Currently it is -29 as I write this and not predicted to warm up before Monday.
There are different theories about how this could affect the result.
The frontrunner is former President Donald Trump, while Florida Governor Ron DeSantis, and Nikki Haley, who served in Donald Trump's cabinet, are other top candidates.
The turnout might be lower than predicted.
It may mean the core Trump supporters, who tend to be older, might choose not to risk the roads.
It might also dissuade young voters, who Haley needs, from braving the deep freeze.
The latest and most significant survey, the Des Moines Register Poll, which came out late Sunday, had Trump on 48%, Haley at 20% and DeSantis on 16%.
There seems little doubt Trump will win here but if he polls less than 50%, it would undermine his claim that he enjoys the support of a majority of Republican voters across the United States and so should be considered the presumed nominee for the party.
But whatever his final tally, he’s expected to win by a large margin.
Nikki Haley has staked much on performing well in New Hampshire on January 23.
Coming second here would propel her into that race with renewed vigour.
If DeSantis finishes third and the gap between him and Haley widens, there would seem little point in continuing his campaign.
He had polled very poorly in New Hampshire and gambled everything on doing well in Iowa.
In fact Haley has outspent him here, but DeSantis may face a cash crunch if he doesn’t finish second in Iowa.
Looking ahead, South Carolina, Haley’s home state, will be the next significant test after New Hampshire.
Despite the fact that Haley used to be Governor of South Carolina, Trump has even greater support there, thanks to the huge number of Republicans who consider themselves evangelical Christians - a constituency that is supporting Trump far more than any other candidate.
Iowa rarely predicts the winner of the national Republican contest, but this time it probably will.
Trump is so far ahead in other states it would take a political earthquake to stop him winning and securing the nomination.
ITV News' US News Editor Jonathan Wald contributed to this report.
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