Why do politicians reverse their positions?

by Ezra Klein

 This kind of thinking is, according to psychologists, unsurprising. Each of us can have firsthand knowledge ofjust a small number of topics-our jobs, our studies, our personal experiences. But as citizens-and as elected officials-we are routinely asked to make judgments on issues as diverse and as complex as the Iranian nuclear program, the environmental impact of an international oil pipeline, and the likely outcomes of branding China a "currency manipulator."

 According to the political-science literature, one ofthe key roles that political parties play is helping us navigate these decisions. In theory, we join parties because they share our values and our goals-values and goals that may have been passed on to us by the most important groups in our lives, such as our families and our communities-and so we trust that their policy judgments will match the ones we would come up with if we had unlimited time to study the issues. But parties, though based on a set of principles, aren't disinterested teachers in search of truth. They're organized groups looking to increase their power. Or, as the psychologists would put it, their reasoning may be motivated by something other than accuracy. And you can see the results among voters who pay the closest attention to the issues.

http://www.newyorker.com/reporting/2012/06/25/120625fa_fact_klein