More than just mobilizing the youth vote itself, the president's college tour symbolically associates him with an idealistic vision of the future.

These days, if the president isn't taking a victory lap in Afghanistan, he's almost sure to be found with a group of students. Friday is no exception: Obama was scheduled to speak at a high school in Arlington, Va., about access to higher education. On Saturday, he'll officially launch his reelection campaign at college campuses in Ohio and Virginia. And that comes after numerous visits to colleges across the country in recent weeks, where he's been urging Congress to take action to prevent student loan rates from rising.

Much has been made of this as an attempt to reanimate the youth vote for Obama, who famously rallied young people in 2008 but finds them feeling less inspired this time around. It's certainly true that Obama's reelection strategy relies in part on running up his margin among young voters -- he won 18- to 29-year-olds by a 34-point margin in 2008, a 25-point improvement on John Kerry's 2004 margin -- and getting them to turn out, which may be the tougher part.

But the youth vote is a pretty small segment of the electorate to be spending so much time and effort exclusively trying to mobilize: In 2008, 18- to 29-year-olds made up just 18 percent of the electorate (virtually unchanged from 2004, when they were 17 percent); the more narrowly construed college-age vote of 18- to 24-year-olds was just 10 percent of all 2008 voters. If it were all about issue-based voter mobilization, you might expect Obama to spend just as much time at senior centers, talking about saving Social Security.

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What Obama's really doing may be more about optics: the symbolic value of all those pictures and video where he's surrounded by fresh-faced, enthusiastic young adults. Every one of those images, and their repetition, drives home his association with the new generation, the future, and the transformative promise of progress -- the mantle of hope that he's straining so hard to reclaim after a strenuous, wearing first term. It's of a piece with his new slogan, "Forward," and his campaign's portrayal of Mitt Romney as the candidate of the past. The cheering crowds of young people are there to serve as a stirring, hopeful sight to older voters, whether they're remembering their own youthful aspirations or thinking about the future that awaits their children and grandchildren. And it's an effect Romney can't summon, as evidenced by his appearance at an Ohio college last week: Some students appeared to struggle to remain conscious as Romney delivered a lengthy riff on office supplies.

There is a danger for Obama, however: Associating himself so relentlessly with young people could reinforce the persistent Republican attack line that he remains callow, naive, and unprepared for the presidency, and that his opponent is the grown-up in the race. That was a major theme of John McCain's 2008 campaign, and it's being echoed this time around: An ad from the super PAC American Crossroads hits Obama's "cool" as empty and undignified, while the Republican National Committee charges that he's all "hype." Being young and idealistic is admirable; being immature, not so much.