As we near the midpoint of September it's a good time to speculate what form the "October Surprise" (or surprises) in the form of a media hit against the Republican presidential candidate will take this year. In 2000, it was the last minute release of the old news of a DUI violation by Bush. In 2004, it was the double-whammy of the "60 Minutes" attempt to impugn Bush's service in the Texas Air National Guard with forged documents (an early surprise which was launched in September) and the scandal of the missing muntions from the Al Qaqaa facility in Iraq. Thankfully, neither had their intended effect, but we can be sure that an attempt to torpedo McCain late in the campaign will be made.
The most promising avenue for attack in my opinion is to dredge up an instance of McCain using a racial epithat directed at African-Americans. Now, I don't know if there is such an incident out there and I'm not implying that there is any reason to suspect there is, but if there is bringing it to light would obviously be of immense aid to Obama. It would allow him to highlight the sharp contrast between the racist past (McCain) and the allegedly post-racial future. McCain did get some heat (and continues to) for using the "G" word back in 2000. But if the media could come up with any evidence (no matter how thin) of him using the "N" word--no matter how long ago--it would be political dynamite. And given his salty reputation, temperament, and era that he grew up in, it wouldn't be that much of a stretch to imagine that McCain could (again could) have such a skeleton in his closet.
The problem is that no matter how you respond to such a charge, you seem guilty. It's kind of the old "when did you stop beating your wife?". If you say you don't have any recollection of the event, it implies that you used such language all the time. Unless you're absolutely certain that said event did not take place, an outright denial poses the risk that someone can actually prove it and then you're in even worse shape. Even if all the evidence that's presented is a witness who claims that you used improper language thirty or forty years ago, it's a tough accusation to take on (witness what happened to George Allen in 2006 post-macaca). Look what And in the case of the 2008 campaign, it would put all the focus on McCain in a negative light and race, a two-fer for Obama.
If such an incident from McCain's past does exist and the Obama camp knows of it, I would imagine they'll wait for the proper moment before passing it to a friendly media source (should be pretty easy for them to find one). This may not be the only last-minute attempt to derail McCain that we see, but I wouldn't be shocked if something like this pops up come October.