You also have the Team Romney theory that Team Obama is taking reliable voters who would normally vote on elections day, and getting them to early vote...in a way it is similar to burning through cash reserve s to give an appearance.
Romney on the other hand, is trying to get unreliable voters to vote early, and count on the hardcores to show up on Election day. IF that is all true, then Obama probably has the biggest operation of this in Ohio, as does Romney...which could account for some of that appearance different.
In other words, their might be a Romney tidal wave on Election day, and many of those Obama voters ALREADY VOTED.
This of course, puts aside the issue of voting 4 times etc etc.
McCain trounced Obama on election day in 2008, it was just that it couldn’t overcome Obama’s advantage from the early voting.
If anything Romney will rout Obama even worse, and if Obama’s early voting advantage is significantly down from 2008, I don’t see how Obama pulls it out.