If he is the nominee, it will bite him (and all who support him) in the butt. Do you think Hillary is going to ignore this issue? She doesn't need the Mormon vote, but she sure as heck needs the black vote and she will do everything in her power to secure it.
This doctrine is a stain upon Mormonism and those who were Mormons before it was rescinded. Romney was one of those Mormons. He participated in the discrimination against Blacks. So did I when I was a Mormon. The Mormon gospel was not affimatively taken to the black population until after 1978. Even then it was only reluctantly taken to them.
How many blacks do you estimate would switch thier vote from Hillary to Romney if he belonged to some other religion?