The gullibility of the American people seems to be the consistent strategy with stuff like that. Just throwing out completely retarded bullshit like "Democrats are terrorists!" "John Kerry didn't really go to Vietnam" "John McCain has a black baby" etc and hoping that people, somehow, believe it. And, they do.
If it's McCain vs. Obama, you can expect that the two will be personally respectful towards each other, outside of at least a few uncomfortable moments of McCain using Terrorism Rhetoric. However, there will also be the people/groups who are going to milk 'B. Hussein Osama' and 'black baby/Vietnam conspiracies' for all they're worth.
Count on McCain to make several major gaffes on the trail & at the debates.
It's an entirely different story if Hillary gets the nomination, though. Kinda.