About half the states now allow some form of early voting, i.e., where voters can go to a poll and cast their votes prior to election day without regard to restrictive rules on "absentee" voting. Early voting polls are open in many states already.
We think early voting favors Obama and his campaign's elaborate "ground game." Instead of a one-day "get out the vote" push on election day, the campaign can engage in a weeks long effort that truly utilizes all those enthusiastic volunteers. While both sides can do this, Democrats typically have lower turnout numbers in their core constituencies--especially minorities--so there's much greater room for improvement.
Anyway, we reported earlier today that Obama had a lead in the early North Carolina early voting. We now have some data from Georgia as well.
According to a Survey USA poll from Georgia, 18% of the sample (of 547 likely voters) had ALREADY voted. Amongst those voters, Obama leads by 52%-46%. (Note: the margin is closer between the Senate candidates in Georgia, with Democratic challenger Jim Martin leading GOP incumbent Saxby Chambliss by 48%-44% among those who've already voted.) It will be interesting to see how this plays out. While McCain had a lead among "likely voters" who haven't yet voted, we'd say a bird in the hand is worth two in the bush. If something on the order of 30-40% of Georgia voters vote early and Obama keeps a lead of six points, McCain will have quite a deficit to make up on election day.
Similarly, in Iowa, Survey USA reported a couple days ago that 14% of the voters in its sample there had already voted. Among those voters, Obama has an overwhelming lead, 65%-31%.
We'll keep digging around for data on this subject--let us know if you have any other good leads or come across a cogent analysis.