Well put

[otkaznik1]

"If you present negative information about someone and it initially goes unchallenged, you might alter some people's conscious beliefs by challenging it later," he asserted. "But they are left with a negative gut-level feeling that doesn't go away."

"Political feelings, once they are strongly held, tend to be resistant to facts. It's just the result of the way our brains work," ...

http://www.cnn.com/2011/POLITICS/04/27/birthers.evidence/