‘Enthusiasm Gap’ Was Largest in Presidential Swing States
snip
This measure of the enthusiasm gap, however, varied quite significantly from state to state. And there is something very interesting about the states where it was larger.
Exit polls were conducted in 26 states (mostly, where there were competitive Senate contests). The largest enthusiasm gap came in New Hampshire. There, Tuesday night’s voters claimed to have voted for John McCain by a 4-point margin, when in fact Barack Obama won the state by 10 points. That’s a 14-point enthusiasm gap.
The next largest enthusiasm gap came in Indiana; the electorate there shifted from having favored Mr. Obama by 1 point in 2008 to Mr. McCain by 10 points: an 11-point gap.
The enthusiasm gap was 10 points in Nevada, and 9 points in Iowa. It was 8 points in Ohio, Wisconsin, Missouri and Illinois.
snip
-----------------------
Edit: He goes on to say this is actually typical. That the bigger a Presidents coattails the more his party suffers in the mid-term.
http://fivethirtyeight.blogs.nytimes.com/2010/11/04/enthusiasm-gap-was-largest-in-presidential-swing-states/#more-3305