The only one I can think of is that it has seriously lowered expectations for how he'll perform tonight. After McCain's less than stellar last couple of days, pundits will shower him with praise if he manages to stay on the stage for the full 90 minutes instead of dashing off in the middle of the debate with the excuse that he has to go rescue a cat from a tree.
And, actually, now that I think about it a bit more, there's another potential upside for McCain from the tumult of the last few days: It's presumably spared him from having to go through much debate prep. During the primaries, McCain and his advisors concluded that his shaky performances in the early debates were the result of too much preparation; or, as McCain put it to me and a couple of other reporters in an interview last December, of "sitting around a hotel room all day, going over and over the same stuff." He said that over-preparation, combined with too much coffee, made him tense and nervous and too combative--causing him to say stuff like how he'd follow bin Laden to "the gates of hell." Eventually, McCain decided to scale back on the debate prep, cut down on the caffeine, and schedule a town hall meeting for the day of each debate, so as to take his mind off things.
He obviously could have done all that this week--without going to the trouble of suspending his campaign and parachuting into the bailout talks--but maybe the drama of it all will make him more relaxed for tonight. Who knows? I just get the sense that people are now writing McCain's political obit, and as Mike pointed out yesterday, that's usually a mistake.