Based on the evidence of just one campaign, Barack Obama’s magic with youth voters became almost legendary — but he’s not necessarily the favorite to capture the millennial vote again this go-round. In fact, his camp is obviously concerned that the 18-to-29-year-old demographic might escape his pocket: The O campaign today rolled out a major new initiative to target youth voters both on and off college campuses. Of special interest to the incumbent — who’s worried, perhaps, that he can’t count on the loyalty of disappointed former supporters — are the more than 16 million potential Obamamaniacs who were too young to vote in 2008.

Called “Greater Together,” the effort will include a website (supposedly to go live today — hasn’t yet) and “Obama Student Summits” at various colleges in crucial swing states like Ohio and Pennsylvania. (The first such summit will take place Nov. 2 in Philadelphia.) The former executive of Russell Simmons’ Hip Hop Summit Action will be at the helm of the whole gig, with help from Obama’s campaign manager, Jim Messina, who explains the amped-up outreach by reminding us that “the president has traditionally done very well with young voters, and there are several million voters who weren’t old enough to vote in the last election.”

True, true — but why doesn’t Messina just come out and say the campaign is concerned about the president’s growing unpopularity with youth voters? (Rhetorical question, people.) USA Today highlights Obama’s problems with Generation Vexed:

Obama’s standing with younger voters also has dropped amid economic problems that have left young people with jobless rates much higher than their elders. The unemployment rate for 20- to 24-year-olds is 14.7%, and for 18- to 19-year-olds a staggering 23.3%. Growing numbers of recent college graduates have moved back to live with their parents.

In 2008, 66% of voters under 30 supported Obama, by far his strongest age group, according to surveys of voters as they left polling places on Election Day. Last month, his approval rating in the Gallup Poll among that age group dipped below 50%.

What’s more, young voters are the least reliable age group for voting unless inspired by a particular candidate, as many were by Obama in 2008.

Still, that’s not to say the youth vote will go handily to the GOP candidate. Obama proved adept in 2008 at meeting young people where they are — online — and it appears his campaign is prepared to do it again. Plus, BHO’s people see important similarities between the incumbent and the youth whose support he seeks: The younger demographic is diverse and likely to be liberal on social issues, for example.

But the College Republicans, at least, are equally confident in the GOP’s ability to win the youth vote. Research by the non-partisan Generation Opportunity also shows receptivity to a free-market message among young adults. And youth voters who did vote in 2008 have signaled they’re more likely this cycle to research candidates’ policy positions before casting their ballots, suggesting they won’t be swayed solely by charisma.

Still, those 16 million who weren’t even eligible to vote last time might very well prove to be like youth voters throughout history — motivated to go to the polls less by party affiliation or heightened awareness of the significance of this election and more by a candidate’s personal attractiveness. The eventual GOP candidate will have to illustrate his or her youth appeal to draw out support. A little effort in this direction from any one of the Republican potentials would be much appreciated — and, in this particular economic climate in which millennials have suffered disproportionately, unusually likely to pay off.