I think Van Der Blub is right. Abdnor beat McGovern 58%-39% only to be defeated six years later by Tom Daschle, who, of course we all know lost very narrowly to John Thune in 2004. That South Dakota seat is quite volatile. If Hersheth eventually challenged Thune in 2010, who knows...but I digress.
Thune seems pretty popular in SD (at least to me, someone from the outside, so take it for what its worth), Perhaps Herseth is better off hoping Johnson decides to not run again, or that she makes a primary challenge?
It'd be a shame to possibly waste her star power against a guy like Thune (who could probably fend her off in a typical year)...
Well from a preliminary perspective 2010 will be a midterm election with a Democrat in the White House so perhaps Hersheth should sit out that one. She could also run for Governor that year. I don't think a primary challenge to Johnson is very likely. The South Dakota delagation is close and the Democrats would probably lose the statewide House seat. That is the other thing to mention; in South Dakota, North Dakota, Wyoming, Montana and Vermont the Representative is just as well known as the Senators as they represent the entire state and are just as well known. So 69% of South Dakotans already voted for Hersheth.
