An easy way to reach the average voter: Humor. Political jargon goes only so far, but John McCain appearing on Saturday Night Live transends politics. Many independents and undecided voters, I'm sure, like to laugh. But most of all, undecided voters like to laugh at politicians.
It's nice to see that McCain can laugh at himself, and especially since he does it well. Obama can't really make, or take, a joke. John McCain can and what's more, he's actually funny. You can't help but laughing, whether you're a Democrat, Republican, or Independent, when John McCain says he will use the "Sad Grandpa" technique to win votes.
So in the words of John McCain: "Come on, Obama's going to have plenty of chances to be President, it's my turn. Vote for me."