The former president vowed to "take America back" as he cemented his place as the party's frontrunner for November's election.
And the margin of victory put the US and the rest of the world on notice of how popular Trump remains with Republican voters.
It sets up a November 5 contest to be more explosive than Bonfire Night and fraught with complexities.
Both politicians would be the oldest president to win an election.
Biden, 81, who would be 86 by the time a second term finished, has been seen stumbling at events and committing several gaffes.
While Trump, no spring chicken at 77, has 91 criminal charges levelled against him.
But that did not appear to put off voters in Iowa on Monday as Trump saw off his closest rivals Ron DeSantis and Nikki Haley.
He won more than half of the votes in the state, confirming predictions he would begin his third presidential campaign with a telling victory.
In the lowest-turnout caucus in 25 years, voters had endured lifethreatening cold weather and dangerous driving conditions to meet in hundreds of schools, churches and community centres.
Those who ventured out delivered a roughly 30-point win for Trump that smashed the record for an Iowa Republican caucus and tightened Trump's grip on the party's nomination. However, it is still several months before the party's standard bearer can be confirmed.
Denne historien er fra January 17, 2024-utgaven av Daily Express.
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Denne historien er fra January 17, 2024-utgaven av Daily Express.
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FEISTY CHELSEA NOT YET READY FOR TITLE PUSH
Tempers boil over as Blues held by 10 men
HATTON'S HISTORIC HAT-TRICK
Tyrrell's treble with a cause
THE INDUSTRIAL REVOLUTION IS DEAD
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THE star of TV hit All Creatures Great and Small wants original leading man Christopher Timothy to join the show.
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A NATIONAL dentistry crisis has seen people resort to pulling teeth out with pliers while numbed by booze, experts warn.
Serial criminals spared jail despite dozens of offences
SERIAL offenders including burglars and paedophiles are being spared prison despite dozens of convictions for the same offence, shocking figures have revealed.
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MILLIONS of grandparents are going without a holiday so they can give money to help their grandchildren out, a survey suggests.
'It's a witch hunt'...doctor hits back over HRT claims
A MENOPAUSE expert has hit back at a TV show which attacked her for prescribing high doses of hormone replacement therapy.
Cleverly tipped to win in poll of Tory faithful
JAMES Cleverly's bid to become the next Conservative Party leader received a huge boost after a poll suggested he would beat frontrunner Robert Jenrick.
Record arrival in small boats
Nearly 1,000 cross on same day as a boy aged two dies
