Utah is usually reliably Republican turf but in this year’s midterm elections a Senate race in the Mormon-dominated state could see a remarkable upset – and one that could damage the Republican party’s ambitions to capture the Senate.

Independent challenger Evan McMullin, a former CIA agent who unsuccessfully ran for president against Donald Trump in 2016, is seeing his race tighten against Mike Lee, a two-time Republican incumbent who initially supported Trump’s legal challenge to the election but later voted to certify it.

An October poll, commissioned by the Deseret News and the Hinckley Institute of Politics, shows Lee with a four-point lead with 12% of voters still undecided.

Jason Perry, director of the Hinckley Institute of Politics, calls this Senate race the tightest Utah has seen in decades. The race is also unique in Utah’s history because it’s not a traditional Republican versus Democrat challenge.

“McMullin’s candidacy is an experiment and will be the ultimate test to see if a third-party challenger can really take down a well-known Republican in what has been a reliably red state,” Perry said.

McMullin has never held public office. In addition to his service in the CIA, he advised the committee on foreign affairs in the US House of Representatives and was the chief policy director for the House Republican Conference. In order to win, Perry says McMullin will need to get almost all of the liberal voters, all of the independent voters and most of the moderate voters. The most recent Hinckley poll showed McMullin pulling 42% of moderates and 70% of liberals.

Key liberal thought leaders in the state, including conservation activists in the state’s billion-dollar outdoor industry, have endorsed McMullin.

“Lee believes that federal land ownership in Utah is hurting the Utah economy. His opponent, Evan McMullin understands the value of Utah’s public lands,” the Black Diamond Equipment founder Peter Metcalf wrote in the Salt Lake Tribune.

Contrasting McMullin’s growing moderate and liberal support, Lee “owns the conservative end of the political spectrum” because of his reputation as a “consistent fiscal conservative”, Perry explained. His base is solid, he adds, and they show up. Lee’s campaign spokesperson, Matt Lusty, claims the incumbent senator still has a significant lead.

“Senator Lee knows how essential it is for Republicans to regain control of the Senate to push back the disastrous Biden agenda that is crushing Utah families with unchecked spending and runaway inflation – but let’s be clear, Mike Lee is leading this race,” Lusty said. The Lee campaign points to McMullin running as an independent but still receiving Democratic endorsements and funding as a way that he’s pulling the wool over the eyes of the state’s voters.

“President Trump was much less popular in Utah than prior Republican leaders and President Biden is not faring better,” Perry said. “This is why Lee is trying to peg McMullin as a Biden candidate and why McMullin is trying to tie Lee to Trump.”

Though Trump has endorsed Lee, the incumbent senator has strategically attempted to distance himself from the former US president by claiming he voted less in line with Trump than all Republican senators except Rand Paul and Susan Collins, the Associated Press reports.

Lee has secured a string of powerful Utah endorsements, including the governor, Spencer Cox, but missing from that list is Senator Mitt Romney, known for being a moderate Republican who works across party lines.

Earlier this month on Tucker Carlson Tonight, Lee called McMullin a “closeted Democrat”, urged Romney to endorse him, and asked members of Romney’s family to contribute to his campaign. But there is a likely problem: Lee voted against three bipartisan bills that Romney was behind – on gun safety, semiconductor manufacturing and infrastructure – and refused to endorse Romney in his 2018 Senate campaign.

Romney’s lack of endorsement is, no doubt, also part of a ripple effect of how Lee responded during the January 6 attack on the Capitol. In text messages obtained by CNN, Lee offered the White House chief of staff, Mark Meadows, his unequivocal support “to exhaust every legal and constitutional remedy at your disposal to restore Americans faith in our elections” and even tried to connect Meadows with the election-denying attorney Sidney Powell.

Lee later voted to certify the election results.

The McMullin campaign is seizing on Lee’s association with Trump and his role in January 6. “Lee has become the poster child for the politics of extremism and division,” said McMullin’s communications director, Kelsey Koenen Witt. “When it comes to legislating, it’s his way or the highway. And as a result, he gets nothing done for Utahns. After nearly 12 years in the Senate, Lee has only passed 10 bills and a good number of them [were] merely named federal buildings.”

Outside Utah, Lee is perhaps most well-known for placing a hold on 2019 legislation that would provide 9/11 responders compensation, arguing he wanted to ensure the fund had proper oversight to prevent fraud and abuse, the Washington Post reported. In 2016, he was one of two senators to vote against imposing sanctions on Russia for their role in the presidential election. In May, Lee also voted against providing emergency supplemental provisions to Ukraine.

Witt contrasts Lee’s voting record with Romney, who she argues has pursued “good-faith, bipartisan negotiations”. Utah voters, she claims, “are exhausted of the division and party politics”. As a result, the Utah Democratic party and the politically moderate United Utah party, declined to nominate their own candidates for Senate and joined McMullin’s coalition, she adds.