In recent polls, blacks seem to be supporting Obama while women support Clinton. The only reasonable explanation I can see for this is that Democratic women and blacks are, as a whole, sexist and racist. On the outside, they like to create an aura of equality, but when when put to a vote, bigotry makes an appearance.
Certainly not all Democrats are bigots, and there are certainly Republican bigots, too. The difference is that Republicans aren't in a position where it's so apparent. Alan Keyes is the only non-white candidate, but he has a general lack of support--Condoleezza Rice would likely get more support.
The underlying problem is that the Democratic party, like the GOP (Ron Paul and John McCain are very different candidates), consists of separate groups and interests loosely joined by a single platform. The feminist interest is very sexist, and the minority "chocolate city" interest is very racist, but in appealing to the broader group, the party platform has to reconcile these differences and put on a face for the public do see. Meanwhile, Republicans can have WASPs run (Keyes and Romney for flavor) without alienating groups within the party. At least Republicans are discrimating on the basis of supposed morals (Huckabee vs. Giuliani) and government styles (McCain vs. Paul) instead of race and gender.
Double-standard, reverse discrimination, hypocrisy, call it what you will, but the last party that should have a holier-than-thou attitude towards minority and women's equality is the Democrats.