If the Dem plan passes to raise marginal tax rates to 47% passes (which it won't), the GOP will get near to taking control of the House in 2010, with about 10 seats gained due to party switches. There was an interesting piece in the WSJ today, that the Dems control a majority of the hyper wealthy CD districts, and most of those Dem congresspersons are sweating bullets.
There are no permanent alignments, just permanent interests.
A lot of those wealthy districts are also super liberal. They are represented by safer than safe Democrats like Carolyn Maloney, Pete Stark, and Henry Waxman.
But there are also some historically Republican, now Democratic districts that are semi-wealthy or have some wealthy constituents such as PA 6, 7, 8, and possibly 13 or NJ 3 that have a nasty history of railing against taxes. Marjorie Margolies-Mezvinsky (D) lost PA 13 (when it was strictly Montco) pretty much on taxes alone in 1994. These are 5 districts in one major metro area alone.
(KP, please don't have an orgasm) I'll even say if the GOP could run a Melissa Brown (or type) Republican in PA 13, go on the taxes issues in the suburbs then the "neighborhood" issues plus the health care plan that has been twisted to exclude some seniors in NE Philly and that could equal even Allyson Schwartz sweating some bullets. I would not get cocky. Obama is losing steam awfully fast and I could see a mini-1994 in 2010, but I'll also say people are judging Obama too quickly and harshly.