You know it amazes me how republicans are so quick to unite behind Dave McCormick, but weren't willing to do the same in just about every battleground race (except Georgia, North Carolina, and Nevada) last year.
I wonder if part of it is animosity towards Fetterman. GOP donors/operatives feel like losing to Fetterman was less justifiable than losing to Kelly, Cortez Masto, Warnock or Hassan and they only lost to him because Dr. Oz was a cartoonishly terrible candidate. They're rallying around McCormick because they think he could have beaten Fetterman, so they're willing to give him another chance at the Senate.
I'm not necessarily saying all of this is true, but it's worth considering as a possible explanation.