It is probably not racism, as such, that motivates these attacks on Herman Cain. The motivation is far more likely to be politics, but politics makes a prominent black conservative such as Clarence Thomas or Herman Cain far more dangerous to the Democrats than an equally prominent white conservative.
The 90 percent black vote for Democrats is like money in the bank on Election Day. A prominent black conservative who offers an alternative view of the world is a serious danger politically, because if that alternative view has the net effect of reducing the black vote for Democrats just to 75 percent, the Democrats are in big trouble at election time.
In this political context, merely defeating a black conservative at the polls or at confirmation hearings is not enough. He must be destroyed as an influence in the future — and character assassination is the most obvious way to do it.