The Democrats won. Pure and simple. Thinking back neither party offered much of a platform. For the D's it was all about Bush and his 'misguided' war in Iraq. For the R's it was all about the evil that would be Speaker Nancy Pelosi. Toss in the MSM biased views against President Bush and the Global War On Terror - well it's hard to win. And too many voters, who normally vote Republican, stayed home.
And why should they have voted? For the past few years the Republican party spent money. Lots and lots of money on things that weren't necesary and that money had to be borrowed. Fiscal conservatives like myself, who live on a budget, have a hard time with that.
In my opinion the Democrats have ~15 months to show they have a plan. If not - one or both houses will go back to the Republicans in '08 - unless the Republicans show that they don't have a plan.