The Dems entire purpose is indeed to keep attacking President BUsh to weaken the Republicans, to set themselves up for a win in 2008, they don't care what it does to the country.
They think the vicious antiwar stance won them Congress in 2006, so they will continue it and become even more shrill -- watch for hearings after hearings for the next two years.
Many people warned this will happen if the Dems take over and they were right.