The thing in the last post about politicians being consumers of theory reminded me of something. I read "Dreams of My Father" a couple of months ago. I found it very thought-provoking.
Strangely, the least important thing about the book is that its author later became U.S. President. The fascinating aspects are quite independent of that. The book is the best account I have read of the life of a small-time politician: the business of politics and the kind of person who participates in it. On the other hand, the book doesn't tell us that much about the second Barack Obama, the one who became Senator and President. He is a later creation.
Anyway, Obama is a perfect example of a consumer of political theory: he neither has a political theory of his own, nor is primarily motivated by theory. His motivation is "be important by helping black people", and he simply picks the first theory off the top of the pile and follows it. Even where he can clearly see the shortcomings of the theory, he doesn't attempt to innovate or look elsewhere, because that's the theory he has, and that's the movement he's part of. His choices are to carry on or to give up.
That's why it's so important to have a theory out there, rather than a handful of inchoate principles.