First off, it's an open seat. Always contest open seats, no matter how Republican. If you don't fight hard when they're open, you'll never get them from an incumbent.
Second and more important, this particular Republican is so batshit insane that even other Idaho Republicans don't like him. Even other Republican politicians. He's one of those feeps who loudly denounces as "liberal" anyone who disagrees with him on any one issue, no matter how slightly.
Click through to the Swing State link. This guy is so bad his own party hates him. Plus, some of the things they say about him are pretty funny. It seems worthwhile to throw some money here.
