Can Obama count on a big turnout of youth voters to give him the winning edge? I think not.

And I'll tell you exactly why. But first, look at this Slate article on the "youth vote." ("Youth vote" is a silly and inapt term, and Slate appropriately puts it in quotes. You have to be 18 to vote, and the demographic group in question may be young as adults go, but they aren't "youths.")

On Election Day 2004, kids turned out in record numbers: About 4.6 million more people under the age of 29 voted in 2004 than in 2000. Yet 18- to 29-year-olds accounted for only 17 percent of voters—roughly the same as in 2000—because the geezer vote also grew. As a result, youth mobilization was declared a myth, perhaps unjustifiably. "We rocked the vote all right," Hunter S. Thompson said at the time. "Those little bastards betrayed us again."

Of course, organizers are saying this year could be different....

Primary bump: Youth turnout in the primaries saw a huge jump over previous years....

The '06 wave: Speculators wouldn't be so optimistic if it weren't for the Phish-like levels of participation in the midterm elections....

Phish-like levels, from '06? Doesn't that stink by now, even if wrapped in newspaper?

... Students for Obama has organized more than 700 chapters, the campaign says. Groups like Rock the Vote and Campus Progress are also registering voters on campuses....

[We now have a lot of] e-mail, text messages, RSS feeds, tweets, and social networking....

... But in a poll conducted in February by Rock the Vote and the Tarrance Group, 82 percent of voters under 29 said they were likely to vote in November, including 62 percent who called it "extremely likely."

But who knows? Who knows is Slate's bottom line.

Now, what I want to talk about is mass psychology. My theory is that Obama's popularity took off among young people because he hit a tipping point where his very popularity generated extreme popularity. Once it seemed that loving Obama was the thing that was happening, people wanted to be part of what was happening. There was that inspiring "Yes We Can" period last February. Bonding took place. If that feeling persists, perhaps it propels young people to the polls.

But that feeling has dissipated. Obama is no longer the improbable, fascinating newcomer who rises up to conquer the indomitable overlady. He's the familiar, good but flawed politician who found a path to the nomination and is having trouble holding onto what was once a nice lead in the polls. He was so different, he was magnetizing everyone, radiating an exciting aura. Those crowds of young people wanted to be in on that, part of that.

And now there's another newcomer who is fascinating people too, and even if she's fascinating different people, it dims Obama's power to fascinate or it dims the significance of fascination to those who were once fascinated. Fascination itself has lost its aura now that those people -- those uncool people -- are fascinated by Sarah Palin.

So it starts to feel like just another presidential campaign. The reason to vote for Obama becomes not much more than the idea that the Democrats supposedly have better policies than the Republicans. What's the thrill of that? Where's the "Yes We Can" vibe when it's only a politician trying to get elected? What's the big deal about being part of that? The throng disperses.

I predict that unless Obama is already on track to win by a good margin, the young voters won't turn out in droves. That is, they'll be psyched about voting if they think he's a big winner. But if it looks like he's going to lose, there won't be that extra boost of young voters to put him over the edge. They will slip back into their traditional political lukewarmth.