It's hard to say. Ernst and Gardner, for however off-the-rails their political beliefs might be, might just be the two best Senate candidates the Republicans have run in the last three cycles.
Tentatively, I'll go for Ernst. Udall hasn't managed to piss away his recognition advantage entirely, and besides, I think someone who's just a bad campaigner is far preferable to someone who is legitimately a useless, arrogant twit.
I never really thought that Cory Gardner was all that extreme. He seems to be more of a generic Republican than anything in my opinion.
I might perhaps have had him mixed up with Lamborn. I just know he's miles to the right of me.