Which comes and goes every year. In 2008, Obama built an amazing youth movement, the likes of which we haven't seen since JFK. However those "kids" in 2008 aren't "kids" now. They've all grown up and have left college... all that stuff.
Its true that Obama doesn't have the "youth" movement like he did in 2008. I think when you hear these things its some journalist trying to both make a story up and scare the reader at the same time. They never mention where this information is coming from -- that's always a clue that you're reading bullshit.
Others have pointed out that it is unlikely that someone who loved Obama would suddenly vote for Romney or any other Republican just as its unlikely a voter going for Palin (but not McCain) would vote for a Democrat this time around.
Both Palin and Obama appealed to someone "new" to the election process, McCain (and for that matter Romney) do not. That's because both Obama and Palin were considered "young" in political terms. Biden and McCain weren't young and so they appealed to an older set of voters.
Also, it is difficult to believe that there are very many "swing" voters our highly polarized society. Our two political parties have been drawing such stark lines it is impossible to believe that some 1/3 of the voting body is "undecided" and willing to flap in which ever breeze is blowing stronger at the time.
I think it is for that reason the hard right Christians have given up on outreach and have fallen back to a breeding campaign that also is heavy on home schooling. That way they can keep pumping out people brainwashed into their thinking. Which is pretty sad when you think about it. Their whole philosophy and rhetoric is so repugnant they must breed new members to stay a viable political faction.