Racism can be an obstacle for Obama?

Two decades ago, Douglas Wilder saw his 9% advantage in the polls for government elections in the State of Virginia drop to only 0.1% when the votes were counted.

Still, he won the elections, becoming the first black man to be elected governor of a U.S. state. But the tight victory meant that analysts had speculate that he had been a victim of the hesitation of whites vote for a black candidate - also known as the Bradley Effect.

According to theory, some white voters say in opinion polls that will vote for a black candidate, but in the privacy of the ballot box on election day, they choose the name of a white candidate.

Tom Bradley was the African-American governor of Los Angeles where, competing in the elections for the governor of California in 1982, he saw his advantage in the polls evaporate just before the vote, giving the victory to his rival, the white Republican George Deukmejian.

In 1989, the same year that Wilder became the governor of Virginia, David Dinkins was elected the first black mayor of New York, but also saw an advantage of 18 points in the polls to become only 2% on election day.

Could this happen with Obama?

Charles Henry, a teacher from California who is among the first to examine the "Bradley Effect", says that Obama would need an advantage of two digits in the polls to feel confident about his victory.

Other scholars suggest that an advantage between six and nine points may be enough. According to most polls, this is the advantage that Obama has today.

Bradley reverse

Douglas Wilder, now mayor of the city of Richmond, Virginia, and supporter of Obama, thinks that racism should not have as great an impact this time.

"Will it have some effect? Yes. Are there still people that do not give their vote to an african-american? Yes. "

But he says: "America has grown, people have grown."

A survey of psychologist Anthony Greenwald and political scientist Bethany Albertson at the University of Washington, suggests that Obama had benefited from a "reverse Bradley Effect" in 12 states during the primary of the Democratic Party, while the "Bradley Effect" itself was only noted in three.

A study by researchers from Harvard, who analyzed 133 elections for government positions from 1989 to 2006, also showed no presence of a large "Bradley Effect."

A search of the Gallup institute suggests that 9% of Americans are more likely to vote for Obama because of his race, while only 6% say they are less inclined to vote him for the same reason.