The big political story is no change. Obama is still the president, there looks like there will be very little change in the party composition of the Republican held House and Democrat led Senate. Given the polarisation of US parties at the moment, this seems to be a recipe for continued legislative gridlock. The last Congress was the least productive in over 120 years.
The House results, though still not all in, look like the most striking. In 2010 the Republicans won 56% of the seats on 52% of the votes and a 7 point lead over the Democrats. In 2012 they look like they will get still get 54% of the seats on less than a percentage point lead, if any at all. So it looks like the electoral system is seriously unresponsive and biased to the Republicans. This is most likely because of a mixture of incumbency advantage and most strikingly disproportionate Republican power in the Congressional redistricting process.
The results of the presidential election were as expected given the polls. I'm glad to see that predictions from polls did well on average, but there were clearly big systematic differences between polling companies (e.g. Gallup had Romney ahead for most of October and at the end while, Reuters/Ipsos polls tended to be more favourable to Obama). While the predictions run by Simon Jackman, Nate Silver and others are impressive and did well, I would still have been more cautious about the probability of an Obama win given the risks of systematic bias in the average polls (industry bias). While US polls do have a good record, with increasing problems with survey research (declining response rates, mobile-only rates increasing, vagaries of turnout etc) it is getting increasingly precarious trying to estimate election shares of the vote from polls. Attempts to predict the outcome of the 2010 British general election suffered from an average error in the Lib Dem vote intention polls of around 4 points. That kind of difference in the US would have completely changed the story (to either a comfortable Romney victory or Obama improving on his 2008 result). So in truth I was still thinking it was too close to call, for similar reasons given by Andrew Gelman.
Peter Kellner has an interesting discussion of the socio-demographic breakdown of the vote in YouGov polls here. They differ substantially from those in the exit poll here which show much smaller gaps than YouGov do. Regardless of why, Kellner's main point that, from a British perspective, the gaps between men and women, old and young, between ethnic groups and some other bases are startling. The exit poll figures suggest the gaps widened slightly between 2008 and 2012 except for the age gap where the Obama vote among 18-29 year olds looks to have dropped by 5 points, but it is still at 60%. This still looks like a nation divided and polarized.
I'm looking forward to the analysis of what happened (both with the votes and the polls) to come.