Sam Wang again, moving from the effects of cell phones to the effect of race on polls.
The disappearing Bradley effect:
A hot topic among polling nerds is the “Bradley effect,” which occurs when a non-white (usually black) candidate falls short of opinion polls on Election Day when he/she runs against a white candidate. For this reason it has been suggested that support for Obama might be overstated — a hidden bonus for John McCain. Now comes a large-scale empirical study by Harvard political scientist Dan Hopkins. He finds that since the mid-1990s, the Bradley effect has disappeared. His paper is a must-read.