Matt is probably right that the "Obama is arrogant" narrative has probably sunk into the national consciousness by now. In that environment, I think the only thing you can do is turn it around, and make it a positive. One way is to point out that McCain is just coming off as really, really bitter. And it would work, too, because he is acting really, really bitter.
The primary may have been about experience versus change, but the general seems to be about hope versus bitterness. I'm not sure what happened to John McCain to make him so bitter, given that he is a U.S. Senator and worth several hundred million dollars, but he is bitter nonetheless. Electing him would be a demonstration that we as a nation are bitter toward the world, toward the civil rights movement, and toward youth culture. In other words, it would be pretty much the same stuff that conservatives have run on for decades. This time, let's put that out in the open, and stop beating around the bush on it.