While it's possible that the interviewer is just fishing to see if you'll talk about your personal beliefs, IMHO, I think declining to answer altogether is a cop out. While I don't advocate talking about specific ideological beliefs (you end up running the risk of saying something really stupid), I think you can abstract an answer to get around that. Something like, "Wow, what a tough job, I don't envy anyone who has to try to make EVERYONE in America happy all the time. I had this job once that was a little bit like I imagine Congress to be...(fill in anecdote about having to make lots of different people happy). If pushed further after that, I would decline any more specific political talk.