This compares top lines. I think a comparison of turnout model accuracy would be more informative. Most of the models that erred predicted that the 2012 turn out would lean less Democratic than the 2008 turn out model, based on the 2010 mid-term turnouts and a (mis)perceived dampening of enthusiasm among Democrats and increased enthusiasm among Republicans. Based on exit polling, there was a drop off of 7 million white voters, and I don't think anyone who predicted that.
The reasons for the low turnout will be interesting to hear. Nationally, nearly 3 million fewer votes for Romney in '12 than McCain in '08, and around 10 million fewer votes for Obama. Polls showed the election to be fairly close, so that would not tend to explain either "giving up" or "overconfidence" as a reason person didn't vote.
