Will Racial Prejudice Hurt Obama? No One KNows.

The truth is that there are so many variables and not enough information. We've never had an African American presidential nominee before. We don't know whether local effects are different from national effects, and whether a national conversation about race and voting will trigger the type of implicit associations that cause some whites to vacillate about Obama.

Social science offers some clues, but they are thin gruel -- the Bradley effect seems to have dropped off in black-challenger/white incumbent races since 1996; implicit racial prejudice exists; Obama did not experience a "Bradley effect" in the primaries, although tens of thousands of voters admitted to exit pollsters that race influenced their vote against Obama.

But these tell us next to nothing about what will happen in the general election.