Paul Davis is not a great candidate - he'll excite the base, but in order to win he needs Republicans to cross over, and he won't be able to do that.
Brownback will win by a pathetic margin, but I'm sure he will win. I would say 53-45. It's worth noting that only 51% of Republicans approve of Brownback here - I'm sure most will come home to him at the end of the day.
They also have Pat Roberts at 35% approval rating, and Moran at 38%. I have a hard time completely buying those numbers.
Shutdown impact.
Perhaps.
Davis needs to win just about all of the Independent and Democratic vote, plus a little bit of Republicans. Considering that a good chunk of these disapprovals come from dissatisfied Republicans who would still prefer him over the liberal Davis, I think he'll be OK. Kansas is one of the few states where an incumbent can win with approvals in the 30's. Meh :/