I fear I'm taking this too seriously, but given the way even the stated party allegiances and commitments have shifted even in the last few years - leaving aside what happens to parties when they get too near power, money and the upper echelons of the Civil Service - it seems a bit daft to talk about party names as though they connote anything at all. I think JMS pretty much sewed up the whole party thing with the Drazi. ("Green!" "Purple!") And I think the Doctor, in any of his incarnations, would have seen right through it. By all means contend that the Doctor's a liberal by nature, but a Lib Dem? I can't see it.

That said, I'm quite sure the Doctor's an anarchist, at least emotionally. A common thread has always been that nobody should have the kind of power he was given by accident of birth, still less that wielded by his species. That kind of thing tends to rub off after a while - and when Ten forgot it, a bullet through someone else's brain reminded him. (There's also a note of power being a huge burden, and one he neither trusts anyone else to carry - especially when they want it! - nor wishes to subject them to suffering.)

Not to mention that the Doctor is the archetypal non-joiner. :)