Several commenters on my post about Sarah Palin's advantages in tonight's debate made variations on the point that, regardless of how Palin does, Joe Biden has an opportunity to shine. And it's true.

About 90 percent of the speculation about the debate (including my own) has centered on the question of how Palin will perform. (Will she crash and burn as horribly as she did in the Couric interviews? Are expectations so low she can't help but exceed them?) And even the 10 percent that's focused on Biden has been overwhelmingly defensive: Will he gaffe badly? Will he seem condescending? Can he please please please keep his answers short and focused on John McCain?

But the fact of the matter is that, for many voters--and presumably "undecideds" in particular--tonight will be by far their most in-depth look at Biden. And while many know that he's a longtime senator and a foreign-policy maven, they may not know about his fluency on economic matters, his blue-collar roots, his sense of humor, etc., etc.

In last week's presidential debate, the clear split between the way elites scored it (John McCain won) and independents and undecideds scored it (Barack Obama won) was, I think, largely a product of differing expectations. Elites, who'd marveled at Obama's poised, efficient campaign for months and saw McCain as increasingly testy and erratic, were surprised the former didn't do better and the latter worse. For many undecideds, though, McCain was still the experienced old hand whose name they'd been hearing for a decade and Obama the flashy, untested new guy with the funny name, so their expectations--and ultimate response to the debate--were reversed.

Now, I think it's still true that Palin's performance tonight is likely to be the more crucial--if she craters, she's done; if she does even marginally okay, she'll stop the bleeding. But there may again be a difference between elite and voter expectations similar to the one that prevailed last week. Among other factors, I suspect many undecided voters feel they know more about Sarah Palin at this point than they do about Joe Biden.

Could Biden screw the debate up badly with a series of gaffes or a bout of senatorial bloviating? Sure. But if he's as funny and approachable and casually hyperfluent on policy as he's been at his best, it's possible he could win this thing regardless of what Palin does.

--Christopher Orr