I have not read Thomas Frank's What's the Matter with Kansas?, though I intend to and I think it looks like a pretty interesting piece of work. I have seen/heard/read Frank interviewed in a half dozen or so media outlets in the past month, most recently this afternoon, when he got a few words in edgewise opposite Charlie Rose. In none of those interviews have I seen the interviewer ask what I'd expect would be a glaringly obvious question:
Hasn't Kansas been a Republican state since, like, the Pleistocene epoch?
Take a look at the electoral history. Kansas went for Wilkie over FDR, Dewey over FDR, Dewey over Truman, Nixon over Kennedy, and on and on. The Sunflower State is not so thoroughly GOP as to be a landslide bucker (i.e., Goldwater lost there like just about everywhere else), but if you look back over the history, the period of late-nineteenth-century populism Frank is interested in looks like a very rare (and short-lived: thumbs up for McKinley in Old '00) phenomenon. If the Arapaho voting records are ever found, I suspect it'll turn out they were voting Republican too. Since the Democrats' loss of Kansans' loyalties is a central piece of evidence in the book, it's fair to ask when they have ever had those loyalties in the past.
Although Frank is for pretty much everything I'm against (He's hostile or indifferent to the few lifestyle and foreign policy issues where the left occasionally makes a useful ally, and on economics he's just this side of the Anti-Masonic Party), I'm not criticizing him for this. His book may well provide an interesting answer to this question. But it's telling that in interviews nobody seems to have thought to ask it.