The truth is that you cannot understand them anymore than they can understand you. If you are really interested you could read Moral Politics : How Liberals and Conservatives Think by George Lakoff or Don't Think of an Elephant: Know Your Values and Frame the Debate--The Essential Guide for Progressives by the same author. The first book in particular will help a little in explaining why the facts are not good enough for most conservatives. The generally will tend to ignore them when they do not meet their version of the world.
I am not voting for Bush, mainly for the slew of lies and excues and the mess he is leaving my kid with social security and the debt. But I know many people that can look past all of that (or ignore it) and are voting for him anyway.