President Obama may still have the support of the youth population, but will they turn out to vote for him? A new poll indicates that is uncertain.

A Gallup poll conducted earlier this week surveyed voter registration and likelihood to vote, broken down by age groups. Among the 18-29 set, 60 percent indicated that they are registered to vote. Obama enjoys a wide lead over Romney in this age group: 64 percent support Obama while only 29 percent support Romney. However, when asked if they definitely will vote in the general election, only 56 percent replied yes.

Comparatively, every other age group surveyed-30 to 49, 50 to 64 and 65 and over- had a yes response rate of 80 percent or more.

The youth vote is important to the Obama re-election campaign, as is evident from President Obama's "college tour" in Colorado, North Carolina and Iowa this week. The Obama message for the week has focused on student loans, but his choice of college campuses in key swing states he carried in 2008 illustrates the importance of the young voters to team Obama.

Obama ran away with the youth vote in 2008: Voters between the ages of 18 and 29 chose him over McCain 66 percent to 32 percent, exit polls showed.

The actual percentage of young voters who turned out in 2008 was not much higher than in previous years: In 2008, 18 percent of the electorate was comprised of voters between 18 and 29. In 2004 that age set made up 17 percent of the electorate. The same was true for 2000. John Kerry and Al Gore won the youth vote in those years as well, but their margins were nowhere near Obama's.

To be sure, the youth vote isn't necessarily make or break for the campaign. In 2008 Obama carried every age group except for the 65-plus set, and the Gallup poll indicates that Obama still enjoys a lead among these same groups in a Romney match-up.

Still, as ABC's Amy Walter noted earlier this week, Obama's percentage of the youth vote in key swing states like North Carolina, Virginia and Florida grew substantially from that of  John Kerry in 2004, no doubt helping him carry these important states and ultimately claim victory. If that group doesn't come out to support him this time around, that is definitely a concern.