The polls were fine, in general. Some polls were off. Nate Silver was able to hit the result based on the poll information - so don't blame the polls.
This.
Maybe I'm having amnesia from six months ago, but what is the currently accepted explanation for why Obama overperformed all the national polls?
4 million conservatives never showed up to vote. They may have overestimated their chances or decided that a non-Christian candidate wasn't worth their time. Polls always show Democrats winning which is why I was so stunned on election night after seeing Romney winning for the weeks leading up to the election.
The mirror opposite of October 2004. A Democrat back then insisted that Kerry was ahead in Ohio after the debates and that he was tied in Wisconsin and exit polls showed the mirror opposite of what the final vote was. What happened was that 4 million progressives stayed home and 4 million conservatives got off their ass. For weeks thereafter, simply because of the perceived solidarity and size of the Religious Right, there were many allegations of voter fraud in the liberal blogosphere from when Ohio was made "green" to when the recount in Ohio was done.
In reality, it was just a controversial and ideological president whose opponents' hatred neutralized their ability to come up with their own ideas (nevermind that the country was too deep into the president's policy to do anything different) and as a result, a president that should have lost by 3 million votes and 30 EVs won by the same margin. Make 30 EVs into 130 EVs and you get the 2012 election.
