Anything can happen.
Scenario 1: McCain loses massively, President Obama is an extremely popular President and the 2010 midterms are similar to the 1998 midterms and aren't too significant. The Republicans nominate a solid conservative and they lose to Obama in a 1996-type election.
Scenario 2: McCain loses narrowly, President Obama begins to sag under continued public disapproval of all types of Government, and has an approval rating of 40%. 2010 is a disaster for the miffed Democrats and the revitalized Republicans make gains. A conservative Republican, possibly the 2008 VP candidate, defeats President Obama in 2012.
Hmmm....
McCain didn't loose narrowly.
