Probably tough for McMullin but I don't know if you guys realize that Lee is not actually popular in Utah. He's being challenged in the primary and last I saw hasn't polled at 50%. Someone correct if I'm wrong of course, but if I was McMullin I'd absolutely be shooting my shot.
McMuffin could barely crack 20% of the vote against Donald J. Trump, the worst Republican fit for Utah in known history.
Also, Mike Lee is an electoral monster in Utah who won 70% of the vote with Trump on the ballot. (Granted, his opponent was literally a transgender running in UTAH).
He's not an electoral monster, a Transgender in Utah who ran against him got more than Clinton. McMuffin cracked 20% of the vote after like less than a month of campaigning.
I always find this twist of McMullin's name to be an interesting insult. Trump was apparently the one who coined it. But otherwise, your point is correct, by and large. In 2016, Lee got you would expect a Generic R to receive in Utah. His overperformance over Trump can be explained by the fact that he won virtually all of the McMullin voters, most of whom are conservative Republicans and most of whom loyally supported that Party downballot in that year.
Gary Herbert, who won his second and final full term as Governor that year, also got most of the McMullin vote. Nevertheless, in the years since, some of the McMullin vote has peeled away from Republicans, as Mitt Romney in 2018 and Spencer Cox in 2020, while still cracking 60%, both did worse than Lee and Herbert, and Trump himself "only" got 57% against Biden. I expect for Lee to do worse than in 2016, although he should crack 60% again.