And what about Florida, where the averages were off by two points? And Ohio, where we know there was massive voter fraud. It doesn't need to be a massive nation-wide conspiracy, just a focused campaign of cheating in targeted swing states.
Uh... the aggregated polling was almost spot on in FL:
Predicted: 49.8 / 49.8
Actual: 49.9 / 49.3
Projected: Scroll down to the filter for individual state projections on the right hand side.
http://fivethirtyeight.blogs.nytimes.com/author/nate-silver/
Actual: http://www.politico.com/2012-election/map/#/President/2012/
And Ohio, where we know there was massive voter fraud.
Predicted: 51.3 / 47.7
Actual: 50.1 / 48.2
Obama slightly under-performed relative to polling - the opposite of what would be expected as a result of significant voter fraud.
Does not man that there was no fraud, but IMO it's a pretty convincing demonstration that it was not a significant factor.