In 1983, professor of African American Studies Charles Henry was the first to measure the so-called Bradley effect, named after Mayor Tom Bradley of Los Angeles. Bradley, an African American, led in the polls, but lost his bid for governor. The term refers to a tendency among white voters to falsely tell pollsters they will vote for a black candidate to avoid criticism.
Some analysts insist that the Bradley effect is no longer valid, as both polling techniques and attitudes toward race have evolved since the phenomenon was first studied.
Nonetheless, Henry says that Obama needs a double-digit lead in polls to feel confident about victory on election day. He talks to Alex Chadwick about the possible inaccuracies in poll numbers and how he expects race to impact the election.