Politics are unprincipled. American politics are the most unprincipled. You say that all the time. Therefore, to act on principles would be counter intuitive when faced with a political decision. In fact, voting on your principles this election will ensure that your goals will never be attained. Therefore, making an unprincipled choice in this election would greatly benefit your enlightened self interest.
It's not like I'm asking you to drink hemlock. Just cast your ballot for Mitt. You wont feel a thing.