I think he will run but I just don't see him wining against McCaskill although the overall race will be close with her winning by 2-4 points in the end
Missourians aren't really libertarianish in nature. She'd probably win by closer to ten points than that. She's more Trumpy than Peterson is
That, and many of the more religious voters may not be enthused by how he's an open atheist.
I think that could really hurt him. I think whoever his opponent is in the primary will attack him hard for being an atheist, so I doubt that he would be able to win the primary in the first place.