[flowerplough]

If she’s the nominee, Dems will have a hard time getting 50% of the black vote? Wrong, TN2K. Hillary as Dem nominee might well reduce black turnout, but blacks just won’t vote for Republicans. Hillary’d still get four fifths of the black votes, but the total number of black votes would be greatly reduced. As so many octegenarians and their descendants still worship FDR for “saving the family farm”, blacks likewise still vote for LBJ and his Civil Rights and Voting Rights Acts, even though Democrat LBJ needed Republican votes in the Senate to get the acts past Democrat filibusters.

[Reily]

I think the argument is that they simply won’t vote, not that they will switch party to the GOP.
A non-vote acts in many ways act as a vote for the opposition candidate.

Historically blacks vote in low numbers compared to their potential voting population, but when they vote its overwhelmingly democrat (85-90%).