With young voters less enthusiastic than they were four years ago, some fear that low turnout might hamper Obama’s effort to win reelection. But contrary to popular belief, Obama can actually afford lower youth turnout rates—as long as he still boosts absolute turnout among Obama’s young and disproportionately non-white base.

There’s actually a big catch with the 18-29 year-old age group: 33 percent weren’t even eligible to vote in 2008. The old 18-29 year old cohort is now 22-33 years old, and even mediocre turnout among 2012’s 18-22 year-olds will allow Obama to compensate for decreased turnout among his aging supporters.

According to the exit polls, 18-29 year olds represented 18 percent of the 2008 electorate or 23.6 million voters. If Gallup is believed, the percentage of 18-29 year olds claiming they will “definitely vote” is down 18 percent, falling from 78 to 64 over the last four years. Now, these figures are among registered voters and it's an open question whether these voters will register at the same rate that they did four years ago, but given that there's still time for voters to register and for the number claiming to "definitely vote" to increase, lets just stick with 18 percent for illustrative purposes. 

Let’s further assume that this year’s 29-33 year olds are less likely to turn out by a similar margin and that every year of the 18-29 year old cohort is equally likely to vote. That’s almost certainly not true, but the ’08 exit polls indicate that 18-24 year-olds represented 10 percent of the electorate, while 25-29 year-olds represented 8 percent, which suggests that the youngest of the young voters were about as likely to turn out as their older brothers and sisters.

Even if turnout among these voters is down 18 percent—and that’s beneath 2004, by the way—the total number of young, disproportionately non-white, and Obama-friendly voters actually increases from 23.5 to 25.7 million.

Even in this relatively low-turnout scenario, 6.5 million new 18-22 year olds will enter the electorate and they can go a long way toward helping Obama compensate for declining turnout among ’08 voters or an increase in conservative turnout. If they vote 63-37 for Obama, the president would net-1.7 million voters.

If non-white or young voters turned out at ’08-levels in 2012, demographics would actually ensure that Obama does even better than he did four years ago. These same demographic trends give Democrats a bit of breathing room to withstand modest declines in enthusiasm among young voters without actually falling far behind where they stood four years ago. 

With this in mind, it’s no surprise that Obama opened his campaign at Ohio State University, or that Michelle Obama is holding rallies on college campuses across the battleground states. Today’s college students didn’t vote four years ago, and even an underwhelming turnout from America's most diverse age group could help the Obama campaign make up for losses among voters who have abandoned their cause since 2008.