The Black vote is most Democratic in the Deep South and Northern Cities; in the Outer South and the Midwest, it tends to be more 80/20 rather than 90/10 or 95/5.
What actual evidence is there that the black vote is 80/20 or so in the Outer South/Midwest?
If that's the case, the Jefferson County (the location of the city of Beaumont, the 24th largest city in Texas) is surely going to flip blue.
If Cruz is now leading by only 2 percentage points, I guess that O'Rourke will need to also increase his showing among white voters if he wants to win.