Senator Barack Obama has expressed frustration that racial issues keep rising to the surface in his battle with Senator Hillary Clinton for the Democratic presidential nomination.   In the latest skirmish, a prominent Clinton fundraiser gave up her post in the campaign following backlash over remarks she made about Senator Obama's race.  VOA Correspondent Cindy Saine reports from Washington.

Former New York Congresswoman Geraldine Ferraro has given up her honorary position in the Clinton campaign, after she told a California newspaper that Senator Obama owes his success in the race for the White House to the fact that he is African American.

Ferraro refused to back away from her comments in her resignation letter, saying she is stepping down from the campaign so she can speak freely, and accusing the Obama campaign of using her comments to attack Senator Clinton.  Ferraro was the first woman to run for vice president on a major party ticket in 1984.

Speaking to a group of journalists from more than 200 black newspapers across the country, Senator Clinton distanced herself from Ferraro's statement.

"And I certainly do repudiate it and regret deeply that it was said," she said.  "Obviously, she does not speak for the campaign, she doesn't speak for any of my positions, and she has resigned from being a member of my very large finance committee."

Senator Obama has called Ferraro's comment "ridiculous" and "wrongheaded", but said he did not believe she intended it to be racist.

Obama said a great majority of voters will base their decisions on substantive issues, and that his victories in states across the country show he can draw support from all races and all regions.

Larry Sabato, director of the University of Virginia's Center for Politics, said raising the issue of race could be harmful to both Democratic candidates, but it could hurt Obama more.

"I suppose you could argue that anytime race is raised it hurts Obama more, simply because, in America, the electorate is about 11 to 12 percent African American and for Obama to win a general election he has to win a very substantial minority of the white vote, and he has to win the majority of the Hispanic vote," he said.

Flanked by nine retired military officers in Chicago, Obama challenged Clinton's repeated suggestion that she and Republican candidate John McCain both have the experience to be commander-in-chief of the U.S. armed forces, but Obama does not.

"After years of being told that Democrats have to talk, act and vote like John McCain to pass some commander-in-chief test, how many times do we have to learn that tough talk is not a substitute for sound judgment," he asked.  "After years of a war in Iraq that should never have been authorized, how many more politicians will appeal to Americans' fears instead of their hopes?"

While the Republicans have already settled on Senator McCain as their nominee, the two Democratic rivals now have more than five weeks to fight it out until the next primary on April 22 in Pennsylvania, followed by primaries in North Carolina and Indiana.   Obama currently leads in the total number of delegates and in the popular vote.