Even if the blacks aren't big on him, who cares? Who's going to beat him?
Besides I have a tough time seeing Paterson being insanely popular even among blacks.
That's not what matters. Cuomo faces the danger of black people reacting negatively to his entry on the thought that he's taking away the office from a black. The more he acts entitled to the office, the more likely that event is to occur.
As for the general election, I doubt the Republicans have the candidate to defeat him but don't forget that the Cuomos still have a lot of enemies in NY and the black percentage of the population is not trivial.