US Election:When former Los Angeles mayor Tom Bradley ran for governor of California in 1982, he was ahead in the polls right up to election day but when the votes were counted, he lost, writes Denis Staunton.
Bradley, a Democrat, was black while his Republican opponent was white and political researchers found that his poll lead was inflated by white voters who told pollsters that they would vote for the African-American but changed their minds when they got to the polling booth.
This phenomenon, which became known as the "Bradley effect", reappeared seven years later when Douglas Wilder, a black candidate for governor of Virginia, saw a nine-point lead vanish on polling day, so that he squeaked through with a margin of half of 1 per cent. It has been seen in numerous races throughout the US ever since but Barack Obama's bigger than expected victory in Iowa, which is 95 per cent white, suggests that if the Bradley effect still operates, Mr Obama is immune to it.
Mr Obama is the only African-American in the US Senate but he is part of a powerful new generation of black politicians that includes Massachusetts governor Deval Patrick, Maryland Lieut Gov Anthony Brown, Washington mayor Adrian Fenty and former Tennessee congressman Harold Ford, who is now chairman of the Democratic leadership council.
These new leaders, most of whom are lawyers educated at Harvard or Yale, are less confrontational on racial issues than older figures like Jesse Jackson and Al Sharpton, who were shaped by the struggles of the civil rights era.
Mr Obama has gone a step further, aspiring to transcend the divisions of race, although he is careful to acknowledge that deep injustice and discrimination persist. The depth of Mr Obama's support among Republicans and other conservatives, suggests he is reaching white Americans in a way that no other black politician ever has.
His success in Iowa could encourage African-Americans, many of whom have been sceptical, to support him in the primaries. African-American Democrats are divided between Mr Obama and Hillary Clinton, whom many are backing out of loyalty to her husband. If Mr Obama replicates his success in Iowa in New Hampshire, which is overwhelmingly white, African-Americans in southern states like South Carolina are unlikely to put a brake on his course to the Democratic nomination.