Well, in the state where I live, MD, you have to be a registered republican to vote on the GOP primary. Black registrations are 85% plus for the Dems, I think. So it may not help Cain much in this state for the primary.
I think this article looks beyond the GOP primary.
My bet is many black folks now realize how bad a shot electing Barack Obama was at establishing the idea that a black man has the ability to execute the office of President of the United States with any degree of competence. I think they would be thrilled to be granted a mulligan by GOP primary voters.