In 2010 the Republican turnout was 44 million.
In 2008 the Democrat turnout was 69 million.
In 2010 the Democrat turnout was 39 million.
What that means is the stunning Republican turnout in 2010 represented a fall off of 15 million voters. The Democrat turnout in 2010 represented a fall off of 30 million voters.
(That's based on House votes since not every state had a Senator up for election)
That's a partial answer to why pollsters might well avoid trying to normalize current data on the 2010 results.
Nice explanation and thanks for posting it. I pray the voter enthusiasm trend from 2010 still exists in the swing states. If not, we have reached the point of no return that our founders predicted.