It's difficult to explain but not difficult to answer. The answer is that most people don't vote on the issues or even with any information. They just vote the way they always have or something along similar lines. I suspect it's a frighteningly small percentage of people whose swing votes actually matter in any decently contested election. DC is probably the best example. Almost literally anyone running against Marion Barry would have been a better candidate, but that's not what matters. I'm sure there are examples on the other side as well, though they're probably in smaller places.
