Nate Silver over-predicted Obama’s national vote only marginally. Nate Silver predicted Obama would get 50.8%; currently Obama is getting 50.5%. Who knows, maybe when all ballots are counted Silver will be proven exactly right about this too. In the Senate he was only wrong by 0.5 seats (with a pro-Republican, not pro-Democrat bias).
When Nate Silver’s model was criticized, Paul Krugman become hysterical and wrote “This is really scary. It means that if these people triumph, science — or any kind of scholarship — will become impossible.” This is silly, obviously part of social science is discussing behavioral models and their assumptions. The model is then tested against reality.
Nate Silvers model did a fantastic job against reality in the 2008 election and the harder to predict 2012 election. The only time Silver’s model did not do a great job was the 2010 election. Silver predicted Democrats would keep the house in the summer, and only gave republicans a 30% chance of taking the house with a 60-seat margin, which they ultimately did.