Early voting has edged past the 1 million mark, and although the numbers are still too few to draw broad conclusions, they show a Democratic advantage.

“Registered Democrats are voting at levels that are either equal to or exceeding the 2008 elections as a percentage of votes cast so far,” said political science professor Michael McDonald, who heads the United States Elections Project at George Mason University in Virginia, which monitors data.

In Iowa, the state with the largest share of the electorate voting early, Democrats have a nearly 2-to-1 edge (52 percent to 28 percent) among the 220,000 early votes cast. The margin is narrower when it comes to absentee ballot requests (48 to 30) and Republicans have gained ground there in recent weeks.

In Florida, Republicans have a four-point margin in party registration of early voters (44 to 40), but that is down considerably over their 12-point edge in 2008.

Ohio, the all-important battleground state, is harder to read because partisan registration is not reported. County numbers show increased early voting in heavy Democratic and Republican areas. In Franklin County, home to Ohio State University, where President Barack Obama’s campaign has pushed hard to organize students, 11 percent of the electorate has voted early.

McDonald said that overall early voting in the United States is likely to exceed 2008 levels, when about 30 percent of the electorate cast ballots before Election Day.

“The unknown question here is whether the Obama campaign is simply harvesting votes they would have gotten anyway or are actually activating people who would not have otherwise voted. It’s probably a combination of the two,” McDonald said.

Mitt Romney’s campaign said Monday that with just 5 percent of the expected early vote in hand, it was too soon to assess who holds the advantage. In a statement, Romney political director Rich Beeson called the conclusions “almost as absurd as predicting the outcome of a baseball game after the second out.”

Obama says he’s going back to Chicago next week to vote early, but first lady Michelle Obama has already beaten beat him to the ballot, mailing in her absentee vote Monday.