Explainer-What are the Iowa caucuses and why do they matter?

(Reuters) - Republicans in Iowa will be the first to cast their votes in support of a presidential candidate in the 2024 election when they attend public gatherings on Monday known as caucuses.

Former President Donald Trump is heavily favored to win the caucuses, but there have been last-minute surprises in the past.

Here is a guide to the process and what to expect:

WHAT IS THE IOWA CAUCUS AND WHEN IS IT?

The caucus is a process by which voters in the Midwestern state select their top choice for their party’s presidential nomination. It differs from a primary because it's overseen by the state party, not the state government, and does not require voting at a polling place.

The Republican Party will hold its caucuses on Monday. Iowa Democrats, separately, are choosing their candidate entirely by mail-in ballot this election cycle and will release their results on March 5, Super Tuesday.

HOW DOES THE IOWA CAUCUS WORK?

At 7 p.m. CST (0100 GMT on Tuesday), Republicans will gather in small groups at a neighborhood location – such as a school, a church, or a union hall – where representatives will make speeches on behalf of their favored candidates. There are about 1,700 precincts across the state.

Votes are tallied by secret ballot and delegates to the county convention are selected. The results are sent to the state party and announced when the tallies are complete, typically within a few hours.

No remote participation is permitted. The process has been criticized for excluding voters who may be working or have disabilities that make it more difficult to attend. About 30% of registered Republicans in the state caucused in 2016, the last time there was a competitive race.

Iowa's 40 delegates to the Republican National Convention will be awarded to the candidate on a proportional basis based on the statewide vote. For example, in 2016, U.S. Senator Ted Cruz received the largest share of the vote at 27.6% and ultimately received eight delegates, while Trump, who finished a close second, received seven. The third-place finisher, U.S. Senator Marco Rubio, also received seven delegates.

WHO CAN VOTE?

Iowa residents who are over 18 and registered as a Republican can participate in the caucuses.

WHY DOES IOWA GO FIRST?

Iowa has traditionally gone first because of a quirk of history. After the Democratic Party liberalized its candidate selection procedures following the 1968 election, Iowa was the first state to schedule its nominating contest. Once candidates and the media flocked to Iowa – and spent buckets of money – the state made sure to keep its first-in-the-nation status.

Democrats tried to change the order of their contests, tapping South Carolina, which unlike Iowa has a large Black population, as the first state on its 2024 calendar with a Feb. 3 primary.

But Democrats in New Hampshire defied the national party and fought to keep their place as the first-in-the-nation primary, prompting President Joe Biden's campaign to announce that his name will not be on the ballot for the state's Jan. 23 nominating contest.

Republicans chose to keep their nomination kickoff in Iowa, where nearly 90% of the population is white.

WHY ARE THE IOWA CAUCUSES IMPORTANT?

The caucuses are viewed as the first snapshot of voters' support for presidential candidates. Typically, those candidates will have spent months campaigning across the state, testing their messages and their appeal. Those who don't fare well sometimes opt to drop out of the race.

In the case of Republicans, however, the state has not been a reliable barometer of national support. None of the winners of the last three Iowa caucuses - in 2016, 2012 and 2008 – went on to capture the party’s nomination. That’s largely due to Iowa’s evangelical Christian community, which plays an outsized role in the process and tends to back the most socially conservative candidate in the field.

In addition, given its relatively small population, Iowa sends far fewer delegates to the national convention than a state such as Florida or Texas, meaning that it plays a highly disproportionate role in the nominating process.

(Reporting by James Oliphant; Editing by Colleen Jenkins, Jonathan Oatis and Jamie Freed)