In states where the black population is less than 5%, Obama has a
record of 7 wins, 2 losses and 1 undecided (NM). In states where the
black population is 20% or higher, he is undefeated at 4-0. However, in
states that are between 5-20% black, his record is a fairly dismal 4-10
(with one of those victories being Illinois).
I remember reading about this idea in Clarence Page’s Showing My Color. Page’s example described differing perceptions of native American groups based on how common they were in the community. When tribe A was at 15% they were described as lazy, drunk, etc. Tribe B at 5% was hardworking and generally a model minority. In a different area where the population figures were reversed, tribe B was described as lazy and tribe A was suddenly the model group.
He mentioned the dividing line being at about 15% although he didn’t cover the fact that there also seemed to be an upper bound. The upper bound might not mean that stereotypes have gone away, but that stereotypes are countered by political clout. Also we’re talking the Democratic primary, so the effective clout of African Americans is probably doubled relative to the general election.
This is not to say that voting against Obama is racist, but I do think the politics of race and racism do play into the election. The same is of course true of sex and sexism, but the demographics on sex of course have a totally different dynamic.