3 things in particular:
1) Brownback waited until 2 months before the election to start airing ads of his own defending his record, and the RGA also came in to bail Brownback out and ran ads comparing Davis to Obama, supporting tax increases and stuff like that.
2) It was leaked that Davis was at a strip club in the 90s which was raided by the police for drugs, and given that Kansas is in the Bible Belt, that presumably did hurt him.
3) The Republican wave + the Mega-Hackish Kansas voters
Not really. Maybe on the OK/KS border or near SW Missouri, but otherwise, no.
