Harry Enten discusses the Republican mid-term advantage in his column today analyzes the Republican mid-term advantage. He uses the Current Population Survey for his data. I'm not going to dispute that it has some merit and perhaps less flaws than exit polls, but the survey indicates 132,948,000 votes in 2012. There were around 129 million, a little less if you don't count write-ins, a little more if you do. That's a huge disparity. So for my analysis I used exit polls.
The charts above show the the differences between the 2008 and 2010 electorates based on age and race. The party voting share doesn't apply to either election. It's a breakdown of how the vote would be in an even election. Based on race, Republicans have a 2.9% advantage. Based on age, Republicans have a 2.1% advantage. Democrats won the House vote in 2012 by 1.1%. If 2012 and 2014 are neutral elections, the GOP will win the House vote by 1.0-1.8% in 2014. That's unexceptional, but it should be enough to gain Republicans 5-15 congressional seats in 2014.