Jumpin’ Joe Knippenberg writes:

If in fact 30-35% of the voters will get to the polls early, and if they favor Obama by margins higher than the national polls suggest for the electorate at large (a function, if nothing else, of Obama’s well-funded campaign organization), then the math is hard to ignore. Suppose turnout is 150 million (a conservative estimate, I think). If 30% vote early, that’s 45 million. If Obama gets 60% of the early voters, he starts election day with a 9 million vote lead. At 55%, he starts with a 4.5 million vote lead. Under the first scenario, McCain would have to win 54% of the votes on election day to pull even. Under the second, he’d have to win 52.5% of the votes. Only the second seems even a remote possibility.

I am against early voting on principle (i.e. even if it helped John McCain I would be against it). But this does make the practice even more vexing.

Update: From a reader:

Jonah,
I am also opposed to early voting, but here’s the flaw in your logic. Wouldn’t you assume that the hardcore Obamaniacs are the ones likely to vote early (and often) because they’re so gosh-darned excited? So, even in the absence of early voting, these guys would never vote for McCain. Similarly, hardcore McCain supporters will vote early. The undecideds or soft-Obama or soft-McCain are who is left. Given the polls that suggest McCain’s support is softer than Obama’s, if they stay committed to McCain, and the numbers start moving to McCain, then the pool of who is left goes overwhelmingly to McCain. It’s not like the really excited Obama fans are going to decide last minute to vote for McCain. The leaners might.
Yes, McCain has to overcome those early voters, but it’s not like he ever really had a shot at them, did he?

Technically it’s not my logic but Joe’s. Regardless, I think the reader makes a good point. My own guess is that in state’s with large black populations, early voting really is a boon to Obama. But it remains to be seen whether the practice is unversally good for Obama. For example, as someone who always predicts that liberal prophecies of a tidal wave of youth votes will not pan out — and I’ve always been right — I’m still betting that the Obama Youth corps will not be as impressive as the left hopes.