Nearly one-third of Ohio’s electorate has already voted --1.8 million ballots have been cast. | REUTERS Last-minute early votes trend Dem

An independent analysis of early voting states indicates that late arriving ballots are trending Democratic, adding to President Barack Obama’s desperately needed early vote advantage in critical battleground states.

In 2008, Obama won four battleground states because he dramatically outpaced John McCain in early voting. While Obama has maintained a lead in early voting in most states this year, Mitt Romney and the Republican Party made early voting a high priority and have cut into his margins.


But Obama may have gained early voting momentum in recent days. “For whatever reasons, Democrats seem to be mailing in their ballots later which is boosting the president’s numbers,” says early voting expert Michael McDonald, director of the United States Elections Project at George Mason University.

( PHOTOS: Election Day 2012)

All indicators last week pointed to scenarios in Florida, Ohio and North Carolina where Romney was well situated to overtake Obama in Election Day voting — possibly offsetting any of the president’s early vote advantage.

But McDonald says that there are too many complicated variables still in play to predict what will happen. Chief among them is how many voters actually show up today.

“It looks like Romney may have an edge in North Carolina — if we look at what happened in 2008,” says McDonald. “Obama’s early vote margin is narrower today. But I think North Carolina could be much closer than people think because we don’t know how many Democrats are going to vote today.”

( Also on POLITICO: 5 things to watch on election night)

In 2008, Obama was 21 percentage points ahead of John McCain in North Carolina early voting, and so even though McCain won the balloting on Election Day, he narrowly lost the state. Today, Obama’s early lead is down to 16 percentage points, leaving him less wiggle room.

Early voting is also playing a role in what is shaping up as 2012’s biggest prize and biggest potential nightmare: Ohio. Nearly one-third of Ohio’s electorate has already voted — 1.8 million ballots have been cast — with a recent CNN-ORC poll showing the president with a hefty advantage, 63 percent to 35 percent.

( Also on POLITICO: The best stories of 2012)

The big unknown for analysts is how much of the Republican newfound success in early voting is cutting into the party’s Election Day totals. “What we don’t know is if they are just moving the chairs around,” says McDonald. “Are the people who voted for Romney ‘high propensity voters’ who were going to vote anyway — or are they new? If they were going to vote anyway, then they are coming out of his totals today.”

Both sides insist that their early voters are either newly registered voters or those who rarely go to the polls — and therefore bonus voters.

Democrats in particular claim to have registered hundreds of thousands of new young voters and Latino voters who have cast ballots early — and maintain that they will still have heavy turnout today among regular voters.

Republicans assert, however, that Democrats have merely cannibalized their electorate.

An RNC analysis of early voting in Iowa, for example, claims that although Romney trails Obama by 15 percentage points in early balloting, “Democrats have turned out over 52 percent of their voters” who would have voted anyway today.

By comparison, Republicans “have almost twice as many very reliable voters available on Election Day than Democrats do — — an advantage of nearly 85,000 voters.”

Early and absentee voting has in recent years moved far beyond voter convenience to an intense part of presidential campaigns’ strategy. By coaxing people to vote early, campaigns can get a better sense of how they are doing incrementally, and also alleviate the pressure on their get-out-the-vote operations on Election Day.

Ballots for approximately 32 million people have already been recorded before Election Day. McDonald estimates that there are likely another 14 million ballots in the mail — bringing the total for early balloting in 2012 up to 46 million — or a third of all votes cast this year.