That whole "poor Republicans are stupid because they vote against their own interests" angle is ridiculous. I haven't read "What's the Matter with Kansas" so I don't know how nuanced Thomas Frank is, but I'd hope he is more sophisticated than claiming that unless you vote yourself more government entitlements, you're stupid. The same line of thinking would also say that rich people are supposed to vote against aid to the poor, otherwise they're stupid, because it's against their self interest.
(If you really believe in free markets and economic liberalism, then the problem for you should really be that Republicans haven't delivered, given that they're the party that likes to pretend like "helping particular powerful industries and companies" is the same as "helping capitalism.")
I could just as easily reframe the issue as "Look at those noble Republicans, voting in the best interest of their country rather in their own narrow self interest." Or, "Look at how they vote for their own long-term interests rather than for short-term gain." I wouldn't vote for a "give me a free pony" platform even though I want a pony. Of course, if you believe whatever it is the Republicans are saying, you might believe that you *are* voting in your self interest. Republicans have been very successful at selling the myth of unlimited social mobility.
I support confiscatory inheritance taxes and free education at every level based solely on academic ability and not ability to pay, as well as universal health care and a guaranteed minimum income. All well to the left of Obama, I might add. (And I'm sure I'm to the right of him on other issues.) But not because I think it's mostly in the interests of one class or another, but because I think it's what is in the interest of the country. And I try to acknowledge that people who disagree with me might just do so because they think that their ideas are in the best interest of the country, not because they are evil or stupid. Like Joe Biden says, question people's judgement, but don't be so quick to denigrate their motives.