My stepdad, who gets all of his news from emails, likes to send me a lot of forwards like this one about Obama being a radical Muslim, which apparently ten percent of Americans actually believe. It's not true that he used a Koran when he was sworn in, although that would have been awesome. As you can see, though, he was sworn in with his family Bible, just before posing for creepy pictures with Dick Cheney:

The Koran thing is one of the stories listed on Fight the Smears, although it might be nice to clarify that being called Muslim isn't a "smear," just untrue in this case. Although I get that the people spreading the rumors certainly intend it as a smear. Still, maybe just once in a while, he could add a courtesy "not that there's anything wrong with that...."
I'm not sure Fight the Smears will work so great anyhow; most people don't care about the truth when lies are so much juicier. I think that rather than expecting the American public to be calm and rational, it'd be a whole lot easier to just make up better lies about John McCain. Something with the dark glamor of The Clinton Body Count and the whimsy of "Stephen Harper Eats Babies." I think a Mad Lib would be the best tool for generating ideas:
[VERB] America, If You've Had Enough! By [CREDIBLE-SOUNDING SOURCE]
Conveniently Forgotten Facts: Back in [YEAR] a group of [SCARY FRINGE GROUP] decided that a fellow member named [BOY'S NAME] needed to die.
[BOY'S NAME] was suspected of [NOUN]. He was first tied to a chair and [PAST-TENSE VERB]. When they got tired of [VERB ENDING IN -ING] him, group member [SCARY, VAGUELY FOREIGN-SOUNDING, MAYBE EVEN ***MUSLIM*** NAME] took him outside and put a bullet in his head. His body was later found floating in a river about [SPECIFIC AND THEREFORE MORE ACCURATE-SOUNDING NUMBER] north of [PLACE].
Perhaps at this point you're curious as to what happened to these [SCARY FRINGE GROUP]? In [YEAR], that's only eight years later, only one of the killers was still in jail. The shooter, [REPEAT SCARY-SOUNDING NAME] managed to get a scholarship to [ELITE SCHOOL YOU YOURSELF COULD NEVER HOPE TO GET INTO] and became good friends with none other than [NAME OF POLITICIAN WITH WHOM YOU DISAGREE]. He later became an assistant dean at [ANOTHER ELITE SCHOOL, MAYBE IN A STATE YOU DISLIKE].Isn't that something? As a [DECADE DURING WHICH VIEWS YOU DISLIKE WERE PREVALENT]'s radical you can pump a bullet into someone's head and a few years later, in the same state, you can become an assistant college dean! Only in America!
How in the world do you think these killers got off so easy? Maybe it was in some part due to the efforts of someone who came to their defense...
This person was, like [AFOREMENTIONED POLITICIAN YOU DISLIKE], a radical [MAJOR] student at [AFOREMENTIONED ELITE SCHOOL] at the time. This person is now known as "NICKNAME." He/She is none other than [NAME OF POLITICIAN YOU ***REALLY*** DISLIKE].
And now, as [CREDIBLE-SOUNDING SOURCE] said; "[SOME CLICHE]." Pass this on!
(I used an email about Hillary Clinton as a template. There are lots to choose from, and they're always especially nasty.)