The more educated a Southerner is.. the more likely it is that they will be able to drop the accent or modify it to something less "country" and neutral/Mid-western/Standard.
Ebonics (so-called) is part of the cultural heritage of Africa-Americans and many people not of color speak in a similar fashion down he'ah.
Similarly lots of blacks who migrated northwards for economic opportunity and less prejudicial environments were still somewhat segregated in their neighborhoods and kept the accent as they moved north, even though it might be generations since their families lived in the South.
Double negatives, swallowing one's "Rs" and other things are the way we (southerners) talk, and it's also often the way black folk (a generation ago we'd say "colored folks") talk depending on their personal preference, educational level, and degree of emotional sympathy with certain parts of African-American history and culture.
The fact that Obama is "black" but doesn't have that "Southern" feel (unless he wants to) helped him out ALOT in the elections.
It's alot easier to vote for someone if they don't ring the guilt/fear meter to ten when they speak.
All Reid did was discuss the issue in private candidly. The only reason he's apologizing is because it's politically neccessary. I doubt Obama gives a rat's ass. He's a intellectual and a technocrat.