Thune/Johnson was a Senate race in ‘02, with Johnson winning by @ 500; Thune/Daschle, also a Senate race, in ‘04 had Thune winning by @ 4500. No landslides there, tho I imagine Thune would do better in a re-election race than in a challenge to the very well funded Senate Minority/Majority leader.
There was also the lawsuit (Daschle v. Thune) the night before the election, first presided over by a judge who was Daschle’s lawyer in his first ‘victory’ (like 26 votes) and the lawsuit there. It ended up with it going to the state supreme court in the middle of the night, calling them out in a blizzard. Not a happy SSC.
My mom grew up in SD and even though we lived in CA at the time, we were up watching it online.
Ann Coulter quipped that it was a case of "too many chiefs, not enough Indians."