'Racism, we are not cured of it,' Obama said. 'And it's not just a matter of it not being polite to say nigger in public. That's not the measure of whether racism still exists or not. It's not just a matter of overt discrimination. Societies don't, overnight, completely erase everything that happened 200 to 300 years prior.'

They worry that a campaign that successfully presents Bush as the product of his Hispanic-infused South Florida home could cut into their party's sizable demographic advantage with Latino voters - particularly in hard-fought states such as Florida, Colorado and Nevada.