Just a quick point: the conventional wisdom says that Barack Obama accomplished a lot in his first two years but won't accomplish much in his last four. I think this is about right. But this should scare Republicans a lot. Obama really did preside over some substantial changes during his first term—most notably Obamacare—and that made it fairly easy to appeal to centrists who felt apprehensive about this pace of change.
But if Obama spends his next four years presiding over nothing more than the implementation of laws already passed while simultaneously addressing America's fiscal problems—something that's inevitable given the end of the Bush tax cuts and an improving economy—then Democrats will look pretty good in 2016: steady, sober, and decidedly non-scary. It could be that doing nothing is about the best strategy the party could follow. And Republicans are going to do everything they can to help.