It was a great election if you're a Democrat. Obama won, without too much drama, against all odds, Democrats added two Senators and changes make the incoming class far more liberal than the outgoing group. Locally, my state defeated a Voter Restriction Amendment and gave control of both branches of the legislature to the Democrats, giving us in Minnesota the "trifecta"--Democratic governor and control of both houses of the state legislature.
With all the gains made by Democrats, why did they gain a piddly number of seats in the US House of Representatives? More after the cute orange squiggle!
The answer is Redistricting, pure and simple. The magnitude of the disaster two years ago in 2010 continues to show it's ugly head. Gerrymandering by Republicans cost Democrats chances to make big gains in presidential blue or purple states. Pennsylvania, Ohio, Florida, Michigan, and Virginia were controlled in total by Republicans and despite all of those states going for Obama, gains for Democrats in the House were minimal. Indiana also was controlled by Republicans. Texas, Arizona, and Utah are red states controlled totally by the vote suppressors. Democrats did their work where they got the chance, but that really is only Illinois, Massachusetts and Maryland. California and Washington were redrawn by commissions, so the maximum partisan gain couldn't be extracted.
A nearby example of gerrymandering is Wisconsin. Republicans lost no strength in their federal delegation, plus they regained the state Senate, won by Democrats through recalls. All of this in the wake of an Obama victory in the state.
Because of redistricting, Democrats will suffer all or most of the decade being underrepresented in the House of Representatives. Governors matter, as do state legislatures.