Now that it looks like the final vote tally is going to shake out as Obama 51 Romney 47, it's time to give credit where credit is due and declare the ABC/Washington Post and the Pew Research polls as the most accurate in predicting the final national-vote margin. Their final polls both called the race for Obama 50-47. Note, too, that both these organizations polled over 2,000 respondents in their final looks at the race.
So, how did the other polling outfits fare in their final assessments of the race? I'm glad you asked.
IBD/TIPP 50-49 Obama
NBC NEWS/WSJ 48-47 Obama
Politico/GWU/Battleground 47-47 tie
CNN/Opinion Research 49-49 tie
Monmouth/Survey USA 48-48 tie
Now, to the two firms that fared the worst and, to no one's surprise, we find Gallup and Rasmussen pulling up the rear.
Rasmussen Reports 48-49 Romney
Gallup 49-50 Romney
Notice that every single poll - even the ones that came closest - wound up underestimating Obama's final total, while many overestimated Romney's. So much for the theory that undecideds generally break for the challenger in the actual voting. In fact, I would posit that likely-voter models ultimately work in Democrats' favor on election day, since so many potential Democratic voters seem to get screened out of such polls in the winnowing process, leaving us with a lot more room for turn-out growth than Republicans.
At any rate, congratulations to ABC/WaPo and Pew Research. As for Rasmussen and Gallup, it's back to the drawing-board for you, chumps.