So, So, David Sirota is correct again about the curious, but entirely logical u-shaped relationship between states' black population share and Barack Obama's performance. Obama does well where the black population is low (and therefore racial polarization is low as well) or high (black votes swamp out polarizing effects). Hillary Clinton wins the states with medium-sized black populations where polarization is strong enough to overwhelm the black voting base.
This is why Obama should do well in North Carolina and Indiana should be competitive -- just as the polls as of now suggest.
--Tom Schaller
