A powerful cause of dissonance is when an idea conflicts with a fundamental element of the self-concept, such as "I am a good person" or "I made the right decision." The anxiety that comes with the possibility of having made a bad decision can lead to rationalization, the tendency to create additional reasons or justifications to support one's choices. A person who just spent too much money on a new car might decide that the new vehicle is much less likely to break down than his or her old car. This belief may or may not be true, but it would likely reduce dissonance and make the person feel better. Dissonance can also lead to confirmation bias, the denial of disconfirming evidence, and other ego defense mechanisms.Think of all the crazy lies and contradictions the Republican Party requires ordinary Republicans to accept as truth.
A lot of people simply couldn't stand it and walked away. Those who remain as committed Republican must be suffering terribly. I hope mental health care is included in the planned healthcare reform package.
If you are a suffering Republican, don't be afraid to seek professional help. Many former Republicans recover fully and go on to live long and happy lives.