We seem to be at the point where there are now two credible possibilities. One is that the Clinton campaign is intentionally pursuing a strategy of using surrogates to hit Obama with racially-charged language or with charges that while not directly tied to race nonetheless play to stereotypes about black men. The other possibility is that the Clinton campaign is extraordinarily unlucky and continually finds its surrogates stumbling on to racially-charged or denigrating language when discussing Obama.
I think the Clintons have looked at Obama's growing black support and made a simple calculation. If they can ratchet up their white votes by a constant drum-beat of Obama drug references, and they can ratchet up their female votes by portraying Clinton as a victim of male bullying in the media, then they can eke out a victory. A close victory - you know, the kind of margin Karl Rove prefers. Small, tilted to your base, and with your opponent slimed for good.