Guess what, Gallup, Rasmussen, and ABC polls had Mitt up by 5 to 6% with a week left then Ms. Krispy Donut showed up.
Hey, guess what ... it turns out that Gallup and Rasmussen were oversampling Republicans. The final turnout split ended up being something like +6 in favor of the Democrats.
Also, keep in mind that some states had more than 40% of their votes cast during early voting -- and Obama outperformed Romney in most early voting. A lot of those votes were cast long before Halloween.
The optimistic polls were the ones that did not have D+6 (which more honestly should have been put as R-6).