If (big if) the democrats take control of the House the President can simply veto any of their bills.
I would like to believe the Republicans would hold together to beat back an override, but I don't have that confidence.
Bush will have a difficult time using the veto when he's being investigated by the House in impeachment hearings. Oh yeah, they are going to try and impeach him. They probably won't have the votes but that's their agenda for the next two years. Tie him up.