While Obama is ahead in early raw voting numbers in Florida and North Carolina, voting expert Michael McDonald, a professor at George Mason University, says Romney has effectively closed the gap enough that strong Republican turnout on Election Day could cost Obama those states.

“It’s going to be difficult for Obama to pull enough ahead to win North Carolina to offset what Romney may do on Election Day,” says McDonald, director of the United States Elections Project. “They’re seeing the same numbers I am seeing.”…

The challenge faced by each campaign — and what makes early voting relevant — is to bring voters to the polls early who wouldn’t otherwise vote on Election Day. Republicans claim that although Democrats are leading in early voting in most battleground states, they are simply “cannibalizing” or diluting their Election Day turnout by turning out voters who would otherwise come out on Election Day.

Senior Obama officials aggressively refute this by pointing to the number of first-time voters they have registered in battleground states. In Florida and Colorado, for example, they have registered an overwhelming number of new Latino voters, who tend to vote Democratic. (In Florida, Democrats say the bulk of the new Latino voters are Puerto Ricans, who are more likely to vote Democratic than are Cuban-Americans). In those states, the campaign has used Spanish-speaking volunteers to return repeatedly to the voters it has registered until they have mailed in their ballots or gone to the polls.