(CNN) - Republican voters in Utah head to their county caucuses Thursday, marking the first step in a primary battle that some hope will topple longtime incumbent Sen. Orrin Hatch.
FreedomWorks, a conservative grassroots group, has been targeting the six-term senator over the last year, aiming to play a similar role as it did in the state's 2010 race.
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At that time, the group aggressively worked to help unseat Sen. Bob Bennett in the GOP primary, which later paved the way for tea party favorite Mike Lee to capture the nomination and ultimately win the senate seat.
In a call with supporters, Russ Walker, the federal and state campaign director for FreedomWorks for America, the group's super PAC, said the committee has spent more than $600,000 in this race making the case that Hatch has voted too many times for "big government" policies in Washington.
At more than 2,000 caucuses across the state, voters on Thursday will elect the 4,000 delegates slated to represent them at the state convention in April. If a candidate wins at least 60% of the vote at the convention, then the candidate wins the nomination. However, if no one breaks that threshold, then the top two picks move on to a primary.
The caucuses essentially take the party's temperature for the first time this cycle, offering a sneak-peek of the delegate make-up at next month's convention.
According to Walker, FreedomWorks for America has been forcefully on the ground in Utah in recent months, holding more than 36 town halls criticizing Hatch's record and instructing voters on how to become delegates.
"We're very excited about this race, and tonight is going to be a big day," Walker said.
While the group has not donated money directly to one of Hatch's Republican challengers, former State Sen. Dan Liljenquist, FreedomWorks praised the candidate's work and presented him with the award "Legislative Entrepreneur of the Year" in 2011, shortly before Liljenquist announced his run.
Hatch made headlines Tuesday night when he announced that if he's elected to a seventh term later this year, it would be his last.
Describing it as a "disingenuous" move, DJ Schanz, a FreedomWorks for America volunteer in Utah, said on the call with reporters that the announcement was a sign their "messaging was working."
"It's just a classic case of a wounded bird fluttering," Schanz said.
Hatch has the backing of Republican presidential candidate Mitt Romney, who easily won Utah's presidential contest last cycle. The former Massachusetts governor also starred in radio and TV ads for Hatch in a major ad buy across the state in recent weeks.
Speaking to CNN on Tuesday, Hatch's campaign manager Dave Hansen said his team feels confident heading into Thursday's caucuses.
"We feel very good about where we stand right now," Hansen said.