Democratic presidential contender Barack Obama's relationship with his controversial former pastor, the Reverend Jeremiah Wright, has put the spotlight on race as an issue in this year's U.S. presidential campaign. VOA National correspondent Jim Malone has more from Washington.

Reverend Wright has re-emerged in recent days to become a major distraction for the Obama campaign.

Wright is standing by many of his controversial remarks, including the notion that an oppressive U.S. foreign policy brought about the 2001 terrorist attacks and that the government created the AIDS virus to conduct genocide against African-Americans.

Wright also told an audience in Washington this week that he will not fade into the background if Obama wins the presidency.

"I am a pastor, he is a member. I am not a spiritual mentor, a guru. I am his pastor," he said. "And I said to Barack Obama last year that if you get elected, November the 5th I am coming after you because you will be representing a government whose policies grind under people. It is about policy, not the American people."

On Tuesday, Obama said he was outraged and saddened by Wright's comments, which he called divisive and destructive.

"When he states and then amplifies such ridiculous propositions as the U.S. government somehow being involved in AIDS, when he equates the United States wartime efforts with terrorism, then there are no excuses. They offend me, they rightly offend all Americans and they should be denounced," he said.

The renewed focus on Wright comes at a crucial time in the lengthy and bitter fight for the Democratic Party's presidential nomination between Obama and rival Hillary Clinton.

Obama remains ahead in the delegate count and both contenders face a major test next Tuesday in primaries in North Carolina and Indiana.

The Wright controversy may be hurting Obama's efforts to broaden his appeal among working class white voters, who have preferred Clinton in recent primaries in Pennsylvania and Ohio.

In Pennsylvania, one in six white voters said race was a factor for them in choosing between Obama and Clinton, and three-quarters of those voted for Clinton.

University of Virginia political expert Larry Sabato says voters historically have been reluctant to admit that race can play a role in their decisions.

"The exit polls have been wrong repeatedly during this long primary process, and there are almost always wrong in the same direction. They overestimate Obama's support. Why? Is it because some white voters are leaving the exit polls and either telling the exit pollsters they voted for Obama when they did not, or are they just refusing to participate disproportionately in the exit poll? I think the answer is yes. That is what is going on," he said.

This phenomenon has come to be known as the Bradley effect.

In 1982, exit polls in the California governor's race showed Democrat Tom Bradley, an African-American, was running ahead of his Republican opponent, who was white. Bradley wound up losing the election, and pollsters said they believed some white voters were reluctant to tell them that they were opposed to an African-American candidate.

Expert Larry Sabato says Obama should be wary of the so-called Bradley effect if he becomes the Democratic nominee.

"It is called racial leakage. We have seen it repeatedly in American history, and it is going to demonstrate itself again in 2008. It already has. If Obama is the nominee, he had better be leading by a substantial margin in pre-election polls because he is going to lose some of those percentage points on election day," he said.

But other experts question the extent to which race is playing a role in the Democratic contest.

"I am skeptical that this effect is as large as many people believe it is, at least among Democrats. It might be larger in the larger electorate, which will include a lot of people who would not vote for an African-American candidate, but many of whom would not vote for a Democrat anyhow. And a whole lot of others that we know from surveys suggesting that voting for a woman just as many challenges," said Norman Ornstein, a political scholar at the American Enterprise Institute in Washington.

Senator Obama told Fox News Sunday that he believes race will not be the decisive issue in either the battle for the Democratic nomination or in the November general election.

"Is race still a factor in our society? Yes. I do not think anybody would deny that. Is that going to be the determining factor in a general election? No, because I am absolutely confident that the American people are looking for somebody who can solve their problems," he said. "If I lose, it will not be because of race. It will be because I made mistakes on the campaign trail, I was not communicating effectively my plans in terms of helping them in their everyday lives." 

Several public opinion polls in recent months suggest Americans are more ready for an African-American president than a woman president.

In two different surveys, more than 70 percent of those asked said the country is ready for a black president, compared to just over 60 percent who said the same about a woman president.