Well that could happen, but keep in mind the 2006 popular votte results were 54-46 dor the DEMS. If in 2008 the congressional popular vote shifts by 2 points in favor of the GOP to 53-47 for the DEMs, the GOP will pick up probably 2-5 seats.....there are still some vulnerable GOP seats, but much of the low hanging fruit has been picked by the DEMs.
That's one hell of a big IF, given our continuing involvement Iraq and Bush's inability to articulate a popular message.
The Democrat Congress needs to be spectacularly incompetent in order for them to alienate enough moderates and Independents into voting GOP.