An Oct. 7 Pew Research report found that before the debate, Romney voters were four points more likely than Obama voters to give the election “a lot of thought.” After it, Romney-voter engagement was 15 points higher than that of Obama voters. This enthusiasm gap already expresses itself in voter registration and is now influencing early voting.

In the eight battleground states that register voters by party, Republicans have maintained their advantage or cut into the Democrats’ in all but one (Nevada). Since September 2008, Republicans have kept their registration advantages in Colorado and New Hampshire. They’ve added more new Republican registrations than Democrats did in Florida, Iowa and North Carolina. And they’ve lost fewer voters from the rolls than Democrats did in New Mexico and Pennsylvania.

Republicans are also getting the better of Mr. Obama in early voting. In 2008, Democrats made up 51% of the North Carolina early vote while Republicans were 30%. This year, Republicans have cast 54% of the ballots returned so far, Democrats only 28%, according to state data compiled by George Mason University’s Michael McDonald for his United States Election Project.