What you say about DC firms is true. Hogan and Hartson historically has played both sides of the aisle in its lobbying and political practice, although my impression is it has more dems than pubbies. In terms of the personal politics of the lawyers, my impression is most lean left as most big firm lawyers do.
I don't know if I agree as to the political leanings of big firm lawyers. It's probably a matter of personal experience.
It would be interesting to see how political donations break down by law firm. Of course, I'm to lazy to do the research.