Why is he running as an independent? Why not try a primary challenge?
Because he has a 0.1% chance winning the general as an independent by having all the dem votes + moderate Republicans, whereas he would have had a 0% chance of primarying Lee.
I mean, Joe Lieberman did this exact strategy in 2006 when Ned Lamont defeated him in the Senate primary, he ran under the "Connecticut for Lieberman" party and won with 49% of the vote to Lamont's 39% and the Republican's 9%
But McMullin needs to win like, the endorsement of Mitt Romney, or something like that, in order to win in Utah. Otherwise he risks being a spoiler candidate.