One of the theories is cognitive dissonance—we find it difficult to hold contradictory ideas in our head at the same time. Cognitive dissonance predicts that given the choice between our emotional ties and facts, we'll pick emotional every time. Facts lose.
When Democrats hear the argument that the president can do something about high gas prices, that produces dissonance because it clashes with the loyalties these voters feel toward Obama. The same thing happens when Republicans hear that Obama cannot be held responsible for high gas prices — the information challenges their dislike of the president.
Nyhan and Reifler hypothesized that partisans reject such information not because they're against the facts, but because it's painful. That notion suggested a possible solution: If partisans were made to feel better about themselves — if they received a little image and ego boost — could this help them more easily absorb the “blow” of information that threatens their pre-existing views?
Nyhan said that ongoing — and as yet, unpublished — research was showing the technique could be effective. The researchers had voters think of times in their lives when they had done something very positive and found that, fortified by this positive memory, voters were more willing to take in information that challenged their pre-existing views.
“One person talked about taking care of his elderly grandmother — something you wouldn't expect to have any influence on people's factual beliefs about politics,” Nyhan said. “But that brings to mind these positive feelings about themselves, which we think will protect them or inoculate them from the threat that unwelcome ideas or unwelcome information might pose to their self-concept.”