Ranking the Dems against their districts

Nate Silver has a great post comparing the voting records of House democrats against the political leanings of their districts. He gives a list of the 25 'most valuable' and the 25 'least valuable' Dems -- the ones who vote better than you'd expect given the electorate in their district and the ones who vote worse than you'd expect given their district.

The Blue Dogs are a mix, he finds -- some vote way more conservative than you'd expect, and ought to be challenged in primaries, while others represent districts that you'd certainly think would elect solid republicans.