Well, if you recall. There was a perfectly timed winter storm, "Super Storm Sandy". The week before the 2012 election, Romney was leading in the polls by about 10%. (not that Romney would've been much better), but the week before the election, winter storm "Sandy" hit and for the next 7 days, Obama was on TV all day every day about helping with the blizzard disaster and I think people changed their minds that maybe it wasn't a good time to change leaders.