I think the interesting thing is that people like McCain and Palin really do believe that they are defenders of the good.
Obama also believes that he speaks for the good.
That makes those people effective at persuading others. It's very postmodern. What counts isn't some form of objective Truth but simply sticking to a powerful narrative in ones principles.
I think McCains approach to telling the truth is the "Racical Honesty" one. It's about simply saying what he thinks and drawing emotionally from his core.
The problem is that you need long careful plan to change things to the good and more than simply principles.
Once a principle gets defended people like McCain unfortunatly begin to lie. Even Karl Rove
admits that McCain is lying.
The irony is that possible to speak deeply from your heart about your principles and lie at the same time.
The audience notices that you speak from your heart and you win in our postmodern world.