One Term Pledge

There's talk that McCain's campaign considered, for a time, announcing for president with a pledge to serve only one term. Now that would have out-Baracked Barack:
One Republican close to the campaign said: “It would have been the most selfless act in modern American politics.”
Marc Ambiner writing on the Atlantic's blog, says the idea was considered as a way to differentiate a candidate who couldn't find his footing.

When he formally announced his presidential candidacy last year, Sen. John McCain was inches away from making an unprecedented pledge: if he were elected, he would serve only one term as president.

It could have been an earth-shifting moment for the campaign and the primary. At the time, McCain’s fundraising pace was falling well short of its target and Republicans were not treating McCain as the frontrunner.

Barack's biggest effect on politics may be that everyone will need an "I'm different" gimmick. A way to show that you're flipping the bird to being constricted by convention. This would have been McCain's. But the reasons not to do it were pretty powerful.
Campaign advisers said that, as they discussed the merits of the pledge, the drawbacks were obvious: it might tie McCain’s hand with Congress. It would certainly raise the profile of his heir apparent and vice presidential nominee, who would be treated as a de-facto presidential candidate for McCain’s entire term. And it would draw attention to his age.