I have a few thing to add to Chris Bowers' advice for Barack Obama. Go after McCain's strengths. Do it now and do it at the convention. Let your surrogates off the leash.

What are McCain's strengths?

1) The media loves him. People hate the media. Show well-known pundits drooling over McCain and make fun of them (and McCain). Make McCain the poster-child for inside-the-Beltway-wankerism and out-of-touchness.
2) He's supposed to be a Maverick. Never lose an opportunity to point out how much of an orthodox right-winger McCain is on the issues. Never praise him for some alleged break with his party or independent stance he may have taken in the past. Don't say that he's changed from the maverick he once was. Say that he never was a maverick in the first place.
3) His military record and experience working on issues related to our national defense gives him an appearance of being qualified for the job. Point out how wrong McCain has been on predicting the future. Point it out over and over and over and over and over again.

Unless McCain's strengths are neutered, he will remain in contention. But his weaknesses need to be exploited as well. Chief among his weaknesses are his bad temperament, his poor relations with his senate colleagues, and his horrible reputation with the base of his party. Drive wedges between McCain and the rest of his party at every opportunity. This is the chief argument in favor of including Republicans and former Republicans in the campaign message machine.

McCain's positions on the issues are a weakness as well, but that should take second place to ripping him down off his pedestal and diving a wedge between him and his party.

When it comes to the national meta-narrative, it should be all about how McCain is the darling of the Beltway elite punditocracy, how he's a far-right winger that is indistinguishable from Bush/Cheney (shows no independence), and that he has no power of prediction (he makes horrible judgments). He's hot-tempered and distrusted by his colleagues, and he's showing age-related mental diminishment.

This is tough stuff, but it's all true. And this election is too important to leave things to chance. McCain needs a fist in his mouth every day so that he has no room to maneuver.