This year’s presidential candidates must make final proposals to the people of Iowa, where the first votes for party nominations will take place later.
Polls suggest Republican Donald Trump has a slight lead over Texas Sen. Ted Cruz, but both are well ahead of the rest.
In the Democratic Party, the race is a little narrower, with Hillary Clinton ahead of Vermont Sen. Bernie Sanders.
The nominee from each party will run for the presidential election in November.
Over the weekend, candidates stormed the sparsely populated midwestern state of Iowa in an attempt to woo undecided voters.
The campaign is expected to continue until the start of voting at 19:00 local time on February 1.
Candidates hope to triumph in this first election test, because victory could spark campaign momentum as voting moves to other states.
Among the broad Republican field, recent polls suggest that Donald Trump has a comfortable, albeit uncertain, lead over his main rival, Ted Cruz.
The far smaller field of Democrats – three candidates as opposed to 11 – seems to be more competitive.
Favorite Hillary Clinton has a nationwide commanding leader, but in Iowa she is slightly ahead of self-proclaimed Democratic Socialist Bernie Sanders.
Iowa has an unusual electoral system called Cacus, which includes people who gather in places in the state at 7:00 p.m. local time on Feb. 1.
Democratic voters are divided into groups based on their preferred candidate, but the Republican parliamentary process is more like a traditional vote.
The last Republican winner in Iowa to win the party’s nomination was George W. Bush 16 years ago.
One problem that can have consequences in Iowa is weather.
The National Weather Service is currently forecasting a winter storm to hit the area on Monday night.
Candidates are worried that the coming storm could prevent their voters from appearing earlier in the evening.
Donald Trump joked with his supporters on January 30, saying: “You’re from Iowa!” Are you afraid of snow? ”
The Iowan Act provides for this to be the first “state, territory or other group” to elect delegates to the presidential nomination.
This first vote in Iowa will be followed in the coming weeks by more ballots in 49 other states plus US territories.
The nominee for each party will be elected by the summer, and the next president will be elected in November.