Pollsters and pundits will tell you that the Bradley effect is when voters tell pollsters they'll vote for the black candidate but actually vote for the white candidate.
Tom Bradley, the African-American mayor of Los Angeles in 1982, ran for governor of California. Weeks before the election, newspapers were reporting that he held a double-digit lead in the race. But in the end, he lost a close election to George Deukmejian, who was the white candidate.
NPR's Mara Liasson has a commentary on the subject:
Seven years later, something similar happened to Doug Wilder in his race for governor of Virginia. Public polls showed him up by 9 to 10 points. And he ended up winning — but only by a few thousand votes.
Wilder says that now the U.S. is an "emerging, evolutionary stage" when it comes to race.
"I like to remind people, however, that if the Wilder effect plays in this election, it'll be good because I won," he says.
A lot has changed since then.
In 2006, Harold Ford — an African-American running for a U.S. Senate seat representing Tennessee — received as many votes as pre-election polls suggested he would. So did Ron Kirk, the black mayor of Dallas, when he ran for the Senate in Texas in 2002.
During this year's Democratic primaries, University of Washington social psychologist Tony Greenwald did a study to see if there was a Bradley or Wilder effect at work in the contest between Hillary Clinton and Barack Obama.
What he found was surprising. In a few states — California, Rhode Island and New Hampshire — Obama did worse than polls predicted. But in 12 state primaries, he actually did better.
Those were states that have a relatively high black population, Greenwald says. He says there is a reverse Bradley effect.
"What we think is going on there is that people who get the call to participate in the poll, they're asked to say if it's Obama or Clinton," Greenwald says. "They give an answer that's easier to give in their region, and in that region it's easier to say that you favor the white candidate than that you favor the black candidate."
Even so, Ron Walters says race is playing a role in the campaign.
"The presidency is almost an anthropological leadership position. ... It represents the head of a tribe for many people," Walters says. "They want a president to be like them, look like them, etc. And to that extent, there's a lot of emotional content about who the president of the United States is. … Barack Obama — part of the politics of this election is that he's been trying to overcome that cultural barrier."
The consensus seems to be that while there are people who will not vote for Obama because he's black, there are probably a lot fewer of them who are willing to lie about it to pollsters.