I think scenarios like this underrate the importance of fundamentals. With the economy in free fall, I don't think very many people would care about Obama praising a Communist poet. Vice presidential candidates have very limited impact--most people agreed that Bentsen got the better of Quayle in their debate, but it changed very few votes. ("Only 5 percent of those who voted for Dukakis gave Quayle as an explanation."
http://www.slate.com/articles/news_and_politics/hey_wait_a_minute/2000/06/nobody_votes_for_the_veep.html) And the effects of presidential debates are also questionable. (The JFK-Nixon race was close before the debates and close afterwards.) And in any event Obama was an experienced debater and hardly likely to collapse. (Moreover, after 1984, the final debate was set far enough from Election Day so that the effects of a poor final debate would have time to fade.)
I'm not saying that McCain can't win. But I am saying that for him to win, you have to prevent the financial meltdown of September 2008. Without that I certainly can't see him carrying states like Colorado (+8.95% Obama in OTL), NH (Obama +9.61%) or even VA (Obama +6.30%)
https://en.wikipedia.org/wiki/United_States_presidential_election,_2008
