DAYTON, O.H. - President Obama's top campaign advisers today said early-voting returns in several battleground states show Democrats with an edge over Republicans in courting so-called "sporadic voters," those Americans who would not otherwise vote and could tilt the scale in a tight race.

"We are outperforming our early-vote margins in key states compared to 2008. We're ahead of where we were against McCain, and more importantly, we're ahead of Mitt Romney," said Obama campaign manager Jim Messina on a conference call with reporters. "Romney may be winning more raw votes than McCain did at this time, but look the facts are important here. And the numbers tell a very clear story."

Messina said that the campaign's growth in early-vote margins, borne out both in state election data and in public polling of early voters, is a net gain for Democrats since many early voters are people who likely would not have otherwise voted. The process was widely credited with helping Obama win several swing states in 2008.

"Early vote isn't only taking a finite number of voters and only changing the day they vote. …. What early vote does is help us get out our low propensity voters-voters called sporadic voters-which broadens our universe and frees up more 'get out the vote' resources later, especially on election day," Messina claimed.

"This is about increasing the overall share of people, who may be drop out voters. And our numbers and public numbers are showing that more Obama sporadic voters are voting than Romney sporadic voters, which is a very big piece of business for the total turnout," he said.

Public polls show Obama holds double-digit leads among people who have already voted in Iowa, Ohio and Wisconsin, states where in-person early voting is allowed. Obama also leads in North Carolina.

The U.S. Elections Project at George Mason University tracks all public early voting data HERE .

The data are not considered definitive indicators of the ultimate electoral outcome in any given state, but do provide a snapshot of voter engagement and the campaigns' ability to bank votes ahead of time.

"Here is the most important thing to remember 14 days out: We're tied or ahead in every battleground state, and we're not leaving any place where we are tied or ahead," he said. "Romney has not been able to knock us out of a single battleground, and we've forced him to spend more and more resources in states like North Carolina that the Romney campaign has said they wanted locked up a long time ago."