CHICAGO (CBS)– Hundreds of thousands of Iowa Democrats are expected to turn out to determine who wins the first-in-the-nation contest after the campaign season that began two years ago.

Here’s what you need to know.

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What is a caucus? 

Iowans will elect delegates without ballots. They are not voting for candidates, but instead voting for delegates who support a candidate.

Caucus attendees elect delegates by moving around a room.

Candidate’s supporters move to one part of a room to show support. Candidates need at least 15% of the caucus-goers’ support to win delegates.

If a candidate isn’t viable or does not get 15% they have to find another candidate that is viable.

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New this year: In addition to electing delegates, officials will be tallying raw votes so it is possible for two winners to emerge at the end.

When will the caucuses take place?

The caucuses will take place at 7 p.m. CT on Feb. 3. There are 1,678 precincts accross Iowa that will include school gyms, churches, libraries and other community areas.

Iowa residents unable to attend in person can participate in “satellite caucuses.” There will be 99 satellite caucus sites in 25 other states as well as three international sites.

Who is eligible?

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Registered Democrats in Iowa who will be 18 by the general election in Novemeber can participate. Anyone who pre-registered can avoid standing in longer lines, but you can also register to vote on caucus night.