(CNN) - Mitt Romney will face the biggest test so far in his bid for US Senate on Saturday, when the Utah GOP gathers for party caucuses to decide who will be the party's nominee to replace retiring Republican Sen. Orrin Hatch.
Romney has already secured a spot on the Utah primary ballot by gathering the requisite signatures to qualify. But because of a protracted battle within the state party, Utah candidates can take two paths to the ballot: by participating in the caucus nominating process favored by party activists or by gathering signatures.
Romney has opted to do both, in a nod to party activists who view the signature gathering process as a boon to big-money, establishment candidates.
It's unclear whether Romney will emerge from Saturday's caucus voting as the party's anointed candidate, even though the former Massachusetts governor has put 9,000 miles on his 2002 Chevy truck visiting all 29 Utah counties in the past two months.
Under the party's complex rules, Romney must secure 60% of the delegate vote to avoid drawing a primary opponent in June. If no candidate hits 60%, then successive rounds of voting are held until a caucus candidate reaches at least 40%.
Any caucus candidate who gets 40% of the vote will make it on the June primary ballot, meaning up to two contenders could advance.
Eleven other Republicans are vying for the party nomination, and many of the 4,000 delegates voting Saturday are uncommitted.
Romney is the only candidate to have collected enough signatures to secure a spot on the ballot regardless of the nominating convention, according to Utah's lieutenant governor's office.
Some delegates have supported Romney in the past and are committed to eventually voting for him in the election. But they view the vote Saturday as a symbolic test of their power to control the party's process and to get behind lesser-known candidates who did not opt to collect signatures.
Several sources close to Romney said his odds of notching what amounts to a party nomination were 50-50.
"Tomorrow's outcome has been difficult to predict," said Matt Waldrip, Romney's campaign manager. "Mitt has enjoyed the opportunity to meet with delegates in every corner of the state."
While there was concern among activists that Romney would simply glide to the nomination because he is so popular in Utah, he has unquestionably put in the time.
There is likely to be a roiling fight over party rules before the Senate candidates address the convention. Some Romney advisers and confidants worry that upset delegates frustrated by that fight could make the former presidential candidate a target of their anger.
"He's definitely attacking it like a candidate, and I think that has played well to some of us that were on the fence," said Boyd Matheson, opinion editor of the Deseret News and a former chief of staff to US Sen. Mike Lee. "Some of the delegates will want to punish him because he also got signatures. Because the real battle brewing is about the process."
In addition to holding 30- to 40-person house parties with delegates around the state, Romney has made one-on-one calls to delegates and held weekly tele-town-halls where delegates can ask him about policy.
In his visits to Utah's 29 counties, he has met with county commissioners, sheriff's department officials and elected officials in small towns. Many of the discussions have focused on what those officials view as federal overreach, from endangered species to water and air quality regulations, particularly as they relate to public lands.
Romney's style on the campaign trail has been notably low-key. He has driven around the state with one or two aides, often holding meetings privately rather than under the eyes of reporters.
He drew a pop of national attention in March when he was quoted as saying he was more conservative than President Donald Trump on immigration policy.
The comment was jarring to many who had noted Romney's more moderate and compassionate tone on immigration in his announcement video, but the campaign argued it was taken out of context.
Most Utah Republicans take a more compassionate approach to immigration policy than conservative Republicans in other parts of the country. That is a product not only of the moderate position of the Mormon Church, but also of the fact that the state is facing a labor shortage in industries from dairy to tech.
In the meeting that drew attention, Romney was pointing out that his position on immigration during the 2012 campaign was more conservative than Trump's, because he did not support giving full citizenship to the so-called Dreamers as then-President Barack Obama did. (Romney now says he supports some kind of legal status for Dreamers because of Obama's promises to them).
In meetings with delegates since then, Romney has clarified that he was simply noting his policy differences with Trump, not supporting the President's harsh campaign trail rhetoric on immigration, which he has criticized.
Romney will be the eighth US Senate candidate to speak at Saturday's convention after a random drawing for speaking slots.
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