BOISE, Idaho — Voting in the Idaho Republican presidential caucus is under way across the state, and GOP organizers are reporting a healthy turnout in counties big and small.

In Ada County, organizers closed the doors of Taco Bell Arena about 30 minutes after the 7 p.m. deadline to make sure hundreds still waiting in lines could get inside and cast their secret ballots. GOP officials estimate more than 9,000 people are taking part in the Idaho GOP's first-ever presidential caucus in the state's most populated county.

In other counties, officials estimated 4,500 voters in Bonneville County and 2,500 in Twin Falls County.

"If you're in line by 7, you'll get in," GOP official Rod Beck said of the logjam at the arena on the Boise State campus.

For the first time in decades, Idaho will have a chance to influence a Republican presidential campaign.

The Ada County caucus began with short speeches from supporters of all four GOP contenders, including Gov. C.L. "Butch" Otter rallying supporters to back Mitt Romney. Former U.S. Sen. Larry Craig, was on hand to sing the National Anthem in a duet with a local high school student.

Boise resident Francoise Teal said she is swinging her support for Rick Santorum, the former Pennsylvania senator who has gained momentum in recent weeks and made several stops in Idaho last month.

"This is a guy I'm really hoping and praying for," Teal said.

Idaho, even with its rich Republican tradition and 32 delegates, has traditionally been an afterthought to candidates vying for the presidential nomination. But GOP officials changed the state's schedule last year, opting instead to swap out a May primary for a caucus on March 6, putting Idaho in the same group as nine other states with Super Tuesday balloting.

In more heavily populated counties like Ada, Canyon and Kootenai, GOP organizers expecting large crowds held the event in sports arenas. In smaller, more rural counties, organizers are opting for small venues, such as schools or community centers or unusual places like Jerry's Country Store in Stanley. Several of the state's big, rural counties holding caucuses in multiple locations to avoid long, burdensome commutes.

Caucus participants should also be well educated on the candidates by now.

In the past three weeks, Romney, Newt Gingrich, Ron Paul joined Santorum in making campaign stops in the state. Paul, hoping to make Idaho his first state win, toured the state Monday, with stops in Moscow, Sandpoint and Idaho Falls. He's expected to rally supporters Tuesday in Nampa.

In the other nine states involved in Super Tuesday contests, Mitt Romney claimed victories in Vermont, Massachusetts and Virginia and is locked in tight race with Santorum in Ohio. Gingrich won in Georgia, while Santorum was declared the victor in Oklahoma, North Dakota and Tennessee.