If they take over the House and start impeachment hearings to appease the lunatic fringe. They will also link legislation to an immidiate withdrawl from Iraq. You should take a look at some liberal sites to see what they have planned, it aint sitting on their hands waiting for 2008.
Unless the Senate and President goes along, the House cant do squat. If the Dems shut down the government by linking an immediate withdrawal from Iraq to budget bills etc, dont you think they will get zapped the same way Newt and the boys did when government shut down back in'95 or whatever.
Impeachment will just make the Dems look stupid.