Nate Silver, the Michigan native who has effectively brought serious analysis of polling into the media in the current campaign, has an interesting article at Newsweek debunking the so-called Bradley effect.
The Bradley effect has received much attention over the last few months. It’s named for Tom Bradley, the former mayor of Los Angeles who lost a bid to become the governor of California after the polls showed him with a substantial lead. This led political scientists to surmise that white voters who would not vote for a black man were unwilling to say that to a pollster, thus skewing the pre-election poll results. Many observers have wondered whether that pattern would repeat itself this year.
Silver cites a study by Daniel Hopkins of Harvard, who studied campaigns involving African-American candidates from the 80s to the present day, comparing the results to the pre-election polls. That study found that while such an effect may have existed in the 80s and early 90s, more recent campaigns involving African-American candidates like Deval Patrick and Harold Ford showed no evidence of such a phenomenon. Then he points out that the Bradley effect did not show up during the Democratic primaries:
Then there are this year’s primaries. Everyone remembers New Hampshire, when nearly all polls predicted a big win for Obama, but Hillary Clinton emerged victorious. That was a bad day for the pollsters–and for Obama, who underperformed the Pollster.com composite average by 9 points. (Still, it is not clear that there was evidence of the Bradley effect at work here. Contributing factors to Obama’s loss may have included his “nice enough” comment, Senator Clinton’s teary moment in the diner–and a simultaneous GOP primary, which allowed McCain to pick off some Obama voters who thought their guy was safely ahead.) What fewer remember is what happened two weeks later in South Carolina. In that case, the Pollster projection had Obama winning by 15 points–but he won by 29. That 14-point error was actually of greater magnitude than the mistake in New Hampshire, if less noticeable because the polls hadn’t picked the wrong horse.