About voting against your own interests - George Lakoff has a excellent book out "Don't think of an Elephant!". It is about American politics, but he talks more generally about voter choice as it relates to cognitive science. People like things that appeal to their existing view of the world, that fit within the so-called "frames" in their mind. Neurological studies show that people's synapses will fire in certain patterns when they hear an idea repeated. When that idea is said over and over again, the reactions between synapses are stronger and more frequent. (I'm sure my explanation is inaccurate; Lakoff is a linguist and cognitive scientist, so it's a bit over my head).

So if you have a certain frame of the world -- "Security for the US is a priority", "Washington is inherently corrupt", you'll be drawn to a candidate who uses that language, because what they say literally fits in with the existing patterns in your brain. If a candidate appeals to those frames, you'll generate a favorable impression of him or her. And if the candidate is really good at framing (a lot of US pols are), this general impression becomes more important than the pols' position on issues -- in other words, you'll be readily to vote against your personal interests. (as the blue-collar class did with Bush, etc)