I wonder if in an alternate history, we would see a Obama vs Powell presidential race. I think there are several factors which make it both plausible and implausible.
This year was marked by a remarkably dismal field of Republican candidates. There wasn’t all that much enthusiasm for any of them and McCain pretty much swept in from behind by not self-imploding. If Powell had stayed in the white house in a position of power and kept himself above the political scrum, he might have come out as a very strong candidate.
Also, this year has shown that people from both sides of the aisle were comfortable breaking out of the old-white-male mold for political leaders. If there were any year in which the political climate was comfortable with a black man running as a republican, it would be this year.
On the other hand, the democratic race was extremely tight this year and Powell running might just have sapped enough Obama voters in the primaries that Clinton would now be the democratic nominee.
In short, what combination of circumstances do you think would have had to happen for there to be a Obama vs Powell presidential race and how plausible does it sound?