Hours before Friday night's debate, the spin room at Ole Miss is empty. But the Obama camp is sending out an early memo on its initial spin: McCain's long record on foreign policy puts the pressure on him to deliver.

And lest we dismiss all spin as meaningless, self serving drivel, there is some truth in the observation that McCain cannot afford to stumble on the debate's central themes, foreign policy and national security.

"The centerpiece of John McCain’s campaign has been his more than a quarter century of experience in Washington learning about and debating foreign policy," says the Obama camp memo.

"If he slips up, makes a mistake, or fails to deliver a game-changing performance, it will be a serious blow to his campaign.  Given his unsteady performance this week, he desperately needs to win this debate in a big way in order to change the topic and get back to his home turf."

We're not sure we agree with the spin that McCain has to deliver a game changing performance. He's slipped in the polls, but the race remains close.

Obama, too, has some challenges tonight, namely assuring swing voters he's up to the job of commander in chief. If he succeeds at that, that could be a game changer that swings voters his way. If he falls short or stumbles himself, he'd need an even bigger edge on the eocnomy to trump McCain's "I'll-keep-you-safe" credentials.

We''ll leave it to voters to sort out whether McCain had an "unsteady" week.

But there's no doubt there is a potential downside for McCain should he slip on national security _ and both potential losses for Obama should he stumble, and upside should he look like a commander in chief.

The nationally televised debate starts at 9 pm EDT from the University of Mississippi. It will go 90 minutes and will be moderated by PBS's Jim Lehrer.