A relative recently sent me a version of this e-mail. It's a picture from some years ago of a young Barack Obama meeting with the Kenyan side of his family. The e-mail is entitled "Say hello to the next first family" and contains the text, "This should give you incentive to get out and vote."
Along these lines, check out this tirade.
Assuming that Obama will be the Democratic nominee, I'm guessing we can expect a lot more of this. Yet I think there's an upside to all this latent racism coming to the surface. If I'm remembering Tali Mendelberg's book about the 1988 presidential election correctly, her argument was that Bush's use of the Willie Horton ads on Dukakis worked, but only as long as the racism was subtle. That is, as long as people saw it as an ad about crime, it took a toll on Dukakis. Once the Dukakis campaign pointed out the racist undertones of it, and people began to see the ad as being about race, it lost its effectiveness, and Dukakis' support went back up.
Obama's supporters are seeming very sensitive (rightly) on this subject and they're not afraid to cry bigotry when they see it. The Rev. Wright stuff was working against Obama until he gave that speech and framed it as a discussion about race, and then his ratings went back up again. And so far, Obama is still winning, and a lot of accomplished white people who tried the subtle racial jabs (Gerry Ferraro, Bill Clinton(!)) are walking away bruised. And it's not helping Hillary much, either.