I've been a little surprised by the lack of a good challenger here. Thune narrowly won 6 years ago after narrowly losing 6 years earlier. SD isn't that red a state and Thune is about as conservative a senator there is outside the south or upper Rockies. I recall one of his big campaign claims was swearing could keep the state's big airbase open even without the pull of being Minority Leader like Daschle, but sure enough it closed within a year of his election. Surely there's someone other than Sandlin on the Dem. bench who could give this guy a serious run?
The reason the elections were so close is because of the incumbent factor and also because South Dakota is a Republican state. Anybody other than Herseth would have a very difficult time against Thune (and Herseth would have a hard time too).
Yeah, it's definitely red rather than purple. But SD still has willingly elected Democrats to the Senate and Congress for decades (and not particularly Blue Dog conservatives either). Johnson and Sandlin were first elected reletively recently, y'know. This tradition gave me hopes of a serious challenge to Thune next year, but it doesn't look likely. ):-(