BOISE, Idaho (AP) -- Idaho is one of the most Republican states, but the state Democratic Party has seen participation in its presidential caucuses grow exponentially over the past few campaigns.

Party leaders hope that surge continues Tuesday, and so far the number of people reserving caucus seats online has some counties scrambling to add locations or find bigger venues.

In 2004, the Democratic caucuses drew 5,000 people statewide. In 2008, that number jumped to more than 21,000. Idaho Democratic Party spokesman Dean Ferguson says he expects that many people or more this year.

Caucuses will be held in each county starting at 7 p.m. Tuesday.

Democratic Party leaders recommend caucus-goers arrive at least an hour early to check in.

Participants will listen to debate as they decide among four options: Hillary Clinton, Bernie Sanders, California businessman Rocky De La Fuente and uncommitted.