Well, it's all a spectrum, after all, just like all mental health issues. A perfectly rational person can believe, for example, that a shadowy cabal was behind the assassination of JFK. (They'd be wrong, but that's not the point. And I'm curious if that article even counts JFK as "a political conspiracy theory," because if they do, I think their number is low.) However, eventually, it becomes a real problem. If that's all that you think about all day, or if you've lost friendships over it, or things like that. For most people, it's something they believe but only really act on at election time.