I would say that's not necessarily true if one's perception of interest is not true. I imagine that there are people who believe religiously that my support of certain causes and candidates could result in my burning in hell forever. I, on the other hand, believe that some people vote wrong for other reasons and that they'll be sorry they did. If I'm right, are they voting in their interest? Are they voting both for and against it at the same time? If you vote for "right to life" and your candidate is a hypocrite who seeks an abortion for his mistress, which interest is which? When is the interest calculated? Is your interest in the perceived benefit or the result?