I think it's obvious that if you look at the Clinton-Obama primary, race has been an important determinant of voting behavior. Working class blacks and working class whites have voted in such radically different ways that it's clear that both candidates are securing a substantial racial solidarity vote. Since there are more whites than blacks in most Democratic primaries, racial tensions are, on balance, an advantage for Clinton. But Orlando Patterson's suggestion that the Clinton campaign's 3 AM ad was part of a crypto-racist ploy seems beneath the dignity of an important scholar. This was run of the mill fearmongering, reflecting Clinton's ideas about the politics of foreign policy.
Frankly, I think a lot of the charges of racism against the Clinton campaign have been overstated. Where they've been guilty, I think, is that in their characterization of primary results they've tended to act as if black people just don't exist in the United States so Obama supporters are all highly-educated latte-sipping intellectuals or rich caucus-goers and states with too many black residents "don't count." Speaking merely even as a white person living in a majority black jurisdiction, this is an absurd and offensive way of looking at the world. But the ad's a pretty banal, if disreputable, attack on Obama's liberal approach to foreign policy and not really anything to do with race.
UPDATE: Anti-Clinton charges that I think are overstated, I should say, do not include charges that Geraldine Ferraro is being an ass and wrecking her reputation.