This is NEVER a problem for Democrats, because they have the ULTIMATE pot-sweetener: Government largesse.
Dems have NO PROBLEM promising more and more people a greater and greater share of "government money" that they simply turn around and extort from the general populace in taxes, user fees, fines, bribes, etc.
Just as long as the Dems can identify a large enough group of "have-nots"--people that have never figured out how the American dream works, and that you have to WORK to be "lucky in life's lottery," to use Gephardt's phrase--they are home free.
They can take from those who PRODUCE (who tend to be Republicans) and give to those who don't, who then become their long-term constituency.
They are, even now, working diligently to corrupt the Latino population--historically very hard-working, though not particularly wealthy--into thinking they can sit back and allow Los Gringos to pay the freight. Don't know if it's working, but we'll see.
So, if the blacks finally slip off the reservation, never fear: The ever-resourceful Dems will find SOMEONE to give YOUR money to, in exchange for their sinecures.