The difference in the Clinton mid-term was that Dick Morris pulled Clinton back towards the center and a GOP congress enforced that centrist image halfway through his first term.
Lest we forget, the economy was in much better shape when Clinton was in office. That is the indicator so many of us forget due to our interest in the more minute day to day events. Zero will own the economy by the mid-terms and if it does not turn around by 2012 he will eat it. Add in the increasing number of usually apolitical folks (tea party anyone?) who are worried about our national debt and spending and the trend lines are really bad for the DNC.
Will it get bad enough for the DNC to lose the house in 2010? I did not think it would but now I am starting to have hope. Conservatives are really motivated right now despite the lack of enthusiasm for the GOP.