Birtherism

Mitt Romney's father was born in Mexico. (He also ran for president.) John McCain was born in Panama. I wonder how many birthers know about that? My guess is that if told, they would immediately and correctly isolate the reasons why those facts are irrelevant given other relevant facts. But that doesn't happen for Obama. Absent better explanations, one is justified in supposing birtherism's source is in part racism, in combination with a few other nutty cognitive biases.