I recall reading that Buchanan threatened to run as an independent if Dole picked a pro-choice running mate. If Dole picked Powell as a running mate, would Buchanan run as an independent, and what would the effects of that be?
Powell may be the exception to that rule though. For a Republican, he is pretty liberal. He wouldn't be seen in nearly the same light as say, Ben Carson is. Of course, only being on the ticket as VP, his impact would be limited. He might draw more black voters, but I doubt in enough numbers to offset a run by BuchananBuchanan likely siphons off more votes from Dole than he does from Clinton (although not by a large margin - some Rust Belt voters would switch from Clinton to Buchanan because of NAFTA).
Powell isn't going to help much with black voters. Black Republicans usually don't do well among black voters, and especially not when the top of the opposing ticket is Bill Clinton.