Looking at national exit polls on voting in US House races is tricky -- it isn't a one-to-one correspondence to the number of elected congressmen. But it's something.
In 2004, the national exit polls showed voters barely favoring the GOP in US House votes, by maybe 1%; in reality, the spread was close to 7 percentage points, and the seats went 232-202 for the Republicans.
In 2006, the exit polls showed a Democratic edge of about 7 points, which is right around the actual vote gap, of 53.6% Dem to 46.4% Rep. -- that resulted in a 233-202 edge to the Democrats.
Today, the exit polls show a national gap of around 13 points for the Democrats. How will that translate into seats? We'll soon find out....