By my tracking system, I have the Democrats at plus 25. But if you figure in that most undecided will go for the challenger this year, a likely supposition, then that could add another 10 seats, or a total gain of 35. Right in the Rothenberg range of 30 to 40 seats.
The biggest thing to consider is that because of gerrymandering, in an average election year, there is less than a 10 seat swing (only once in the last 20 years has there been a net shift of more than 9 seats). Thus if the Democrats pick up 35 seats, that will likely guarantee them control of the House for years, probably until a Democratic President is as unpopular as Bush is today.
It could be 20 yrs before the Republicans regain the House...
Awesome.
