Bradley Effect
n.— «The phenomenon was first widely noted in 1982, when Los Angeles Mayor Tom Bradley lost a squeaker of a race for governor after being widely projected as the winner. Douglas Wilder also came up against the “Bradley Effect” when he barely won the 1989 contest for governor of Virginia, after leading comfortably in the polls.» —“The ‘Bradley Effect’” by Ellis Cose Newsweek Oct. 30, 2006. (source: Double-Tongued Dictionary)