He might get bigger swings with some states' blacks than others. The thing to look for is where the AAs in a state are more non-college and low income, I'm not sure yet if there's an urban/rural difference. The Democratic vote is so high with them everywhere but perhaps in some states there is more vote to lose than in others.
I suspect this would be states with larger proportions of rural Afro-Americans and states with a worse educational system than others and institutional racism in its history, which would typically be the south.
Georgia, Mississippi, South Carolina, North Carolina, Louisiana, Alabama, Florida, maybe Virginia (?)