Black Voters vs The Clintons

They did it, and Penn didn't see it coming:

Overall, Clinton lost 100 points of support among black voters in about 120 days: a truly remarkable achievement. Since black voters make up about 20 percent of the Democratic primary electorate, a 100-point swing among black voters translates to a 20-point swing among all voters. And that, essentially, was how the primary was lost. In national trial heats, Obama was polling about 20 points behind Clinton throughout most of calendar year 2007, and wound up polling about 5 points ahead of her for most of the period after Super Tuesday. That is a 25-point swing, and 20 of those 25 points came from black voters.