Say what you want about the GOP win depending upon turnout -- but what if the turnout of 2014 becomes typical for the next two big elections?
Why consider something that's close to impossible? This election had low turnout even by midterm standards. A lot people (disproportionately Democratic) think voting only matters when a president is on the ballot.
Which is a huge, huge problem. What are we going to do about it? Furthermore, what if those voters decide it isn't worth showing up if a Democrat other than Obama is on the ballot because "THEY'RE ALL THE SAME!!!111!!". It baffles me that anyone who lived through the Bush years can think this way, but I know some who do.