I recommend to everyone excellent posts on cognitive biases, misinformation, and partisanship by Brendan Nyhan, who is interested in the question of why people continue to hold false beliefs about Barack Obama, and John Sides, who summarizes some fascinating research. While I'm interested in both cognitive biases and partisanship, I'm far from an expert in this area, so I'll leave it to Brendan and John to feed you the literature, and stick to one quick anecdote. My favorite experience with this was in fall 2000, which happened to be my first time teaching a very large section of an introductory course in American Politics. Of course, we did discuss in class the extraordinary events surrounding the Florida recount. It rapidly turned out that not only did all my students turn out (shockingly!) to have deeply felt beliefs about whether hand or machine methods were the correct way to count (and/or recount) ballots, but they had, or so they reported, held those beliefs for some time. Oh, and (and all this was by show of hands, class discussion, and plenty of after-class discussion) by some amazing coincidence their long-held beliefs about the superiority of human or machine counting lined up almost exactly with their support for either George W. Bush or Al Gore. What I really like about this one was that unlike most policy positions, this one was transparently generated by the partisan situation; of course, in reality none of my students had ever thought for a moment about the best way to count ballots until Election Day 2000, and there is no logical "liberal" or "conservative" position on how to count ballots (that's true of many issues, but was painfully obvious in this particular case). That was not, however, what it seemed like to them at the time.
And part of what makes the topic so fun, at least in my view, is that there's also a bias towards fitting our memories to match our current logic, so I suspect that if I went back to those same students today, ten years later, few of them would even remember passionately holding those positions. Just as many Democrats over the last five years have gone from relative indifference between Barack Obama and Hillary Clinton (and, don't forget, John Edwards), to intense belief that one was The Forces of Good and the other that season's Big Bad, and now back to the original (more or less) feelings about them, all without realizing any inconsistency or, to a large extent, any active change.
Great topic, with lots of fascinating implications for our theories of politics and democracy.