WASHINGTON, Oct 27: Can a white American voter be trusted to vote for a black man when he or she is alone in the polling booth and nobody is watching?

“Yes,” they can be trusted, says Michelle Obama, whose husband Barack Obama is the first non-white presidential candidate of a major American party.

Others disagree.

Former San Francisco mayor Willie Brown says that “race is still a problem in this country” and it could cost Mr Obama several battleground states — and possibly the presidency.

People like him say that when surveyed on issues like race, many people do not express their true feelings because they are afraid of being labelled ‘racist’. But when they enter the polling booth, they allow their real feelings to take over.

American political scientists also have a name for the phenomenon: the Bradley effect. It is named for Tom Bradley an African-American who lost the 1982 California governor’s race despite being ahead in voter polls.

In other races involving a black candidate – most notably Charlotte mayor Harvey Ganttt’s bids against Senator Jesse Helms for North Carolina’s seat in the US Senate in 1990 and 1996 and L. Douglas Wilder’s run for the Virginia governor’s office in 1989 — the Bradley effect came into play. Although Mr Wilder won the race, his votes were far less than predicted.

But Michelle Obama told CNN’s Larry King that a lot has changed since Mayor Bradley lost.

“That’s several decades ago, and I think there’s been growth and movement,” she said. “I just believe that the issues are going to weigh in people’s hearts more so as they go into the voting booths this time around.”

But Mr Brown told CNN that while American voters seemed more focused on issues like the economy and Iraq war, “race could rear its ugly head. I just hope it doesn’t before Nov 4.”

The issue, however, is much more complicated than either Mrs Obama or Mr Brown appears willing to acknowledge.

In a new nationwide survey by Gallup, 88 per cent white voters said race would have no role in determining how they vote on Nov 4. Roughly three-quarters of black voters said the same.

In a Washington Post-ABC News, 87 percent of white voters said they would be comfortable with a black president, including 66 per cent who said they would be “entirely comfortable” with the idea.

But when Gallup asked whether Mr Obama’s being black would gain him more votes than it would lose him, one in every four white voters said it would cost Mr Obama more votes than it would gain him, while 21 percent said the reverse.

Asked how likely it was that each party would use race as an issue in the campaign, 50 per cent of white voters said it was either very or somewhat likely Democrats would use it, roughly the same number (49 per cent) of white voters who said the same of Republicans.

Interestingly, black voters agreed with their white counterparts on the likelihood of Democrats using race as an issue — 48 per cent said it was likely. But they broke with whites on whether Republicans would use skin colour as an issue; 43 per cent of black voters said Republicans were “very” likely to use race as an issue and 27 per cent called it “somewhat” likely — for a total of 70 per cent.