Chuck Todd of National Journal (subscription reqd.) thinks John McCain's main problem is his age (while some readers may speculate that McCain has bigger problems, it is clear that if elected he would be our oldest president).
Todd thinks McCain could possibly overcome the age issue by pledging not to run for re-election. He writes:
"In '03, I wrote a column arguing that some candidate ought to run on the mantra of 'taking the politics out of the presidency' by pledging to serve just one term. Could McCain frame the decision this way?"
From a PR perspective, it just might work. The media would probably eat it up -- simply because it's a novel idea.
But there are other benefits; McCain could cut a deal with someone (such as, say, Mitt Romney) to support him in exchange for serving as his VP (and becoming his obvious successor).
McCain's detractors might also work a little less hard to defeat him if they believe they will only have to deal with him for four years.
Of course, the Founding Fathers never intended for self-imposed term limits such as this. And the downside for McCain would be instant lame duck status ...