A good preview of this will be in the 2013 offyear elections and of course, the 2014 elections.
Midterms have almost no bearing. We all saw how Democrats got massacred in 2010, and they didn't utilize Obama's GOTV machine. Its a personality based voter outreach. The 2010 massacre gave the GOP hope that the Obama machine was done for, and that voter levels would be similar to 2004 than 2008. President Obama has shown how to campaign. He appeals to the best in human nature and gets it. He recognizes that the low-information voters cannot be swayed his way, so he works on the rest. He rightly sees Suburbia as legitimately urban instead of the 'concentrated rurality' of its origins.
FDR won a landslide in 1936. Unemployment under Barack Obama parallels that of Reagan between 1981 and 1984, and we did not get President Mondale.
Democrats will almost certainly keep their Senate majority. There will be some brittle targets in the House -- low-achievers and extremists who didn't face meaningful challenges in 2012 but might be vulnerable.