I'm undecided about principals.
It's good to have things you believe in, but it's bad to get so stuck to them that you can't change.
With all the talk of Romney being a flip-flopper I think that I'd rather have a flip-flopper who listens to what the people want and how they feel (something that can change) than someone like Santorum. Principals are nice but I think you can stick to them without casting yourself in concrete. Times do change.