Seems like kind of a moot point to me, since there's no way that Keyes will win the Senate race. In fact, I can't imagine the Illinois GOP could have come up with a more lame candidate. Almost anyone else would seem to have a better chance than Keyes, who has been a sideshow act for so many years. The only reasons I can think of for them to pick Alan Keyes are:
1) He's black, and they figured no white guy would have a chance against the already popular Obama. This seems like a miscalculation to me though, since the Democrats are going to get almost all of the black vote there anyway. There are a lot of conservatives in southern Illinois, so it seems to me that the most moderate Republican possible would be a better bet.
2) The more likely possibility, I think, is that the GOP has already thrown in the towel in that Senate race and figured they'd throw Keyes a bone and look more diverse. He's been out of the spotlight for a few years and he does seem to have some backers among Republicans. Prominent black Republicans are rare, so the GOP probably figures they need to highlight the ones they DO have. Keyes could get a little bit of press and keep his C-list political career going while the Republicans reload for the next race there.
Like I said, I think it's kind of irrelevant at this point. I can't help but wonder how Mike Ditka would have done though. At the very least, it would have been entertaining. ^_^