The concern is particularly at play for black candidates. It is called the Bradley effect, named after former Los Angeles Mayor Tom Bradley, an African-American, after he ran for California governor in 1982. Some pre-election polls showed Bradley with a lead of 9 points or higher; but Bradley lost to Republican George Deukmejian by a little more than a point.
As the theory goes, people lied to pollsters, saying they would vote for Bradley when they did not.
The Bradley effect could just as easily be called the Wilder or Dinkins effect.
In the 1989 Virginia governor’s race, one poll showed Douglas Wilder with an 11-point lead. He ended up winning, but by less than a point. In the 1989 race for New York City mayor, one poll showed David Dinkins with a 14-point lead. He won by just 2 points.
Some analysts suggest that voters will tell pollsters one thing, because they don’t want to seem prejudiced, and vote differently.