While I understand the comparison Francis is trying to make about political realities with that post, it doesn't seem to me like a very worthy reason to oppose Romney as the nominee. The LDS position on race in the past was certainly bad, but it's not like Romney had any control over it, and I think there are any number of other reasons to oppose Romney that don't smack of bias about where the man worships.
And in any case, if anyone thinks that John McCain will get any more of the African-American vote than Mitt Romney will in a race against Barack Obama, I think they're kidding themselves - 90% or more will go to him. The real benefit for McCain comes from the Latino community, where he has much better footholds than Romney.