I don't disagree that our leaving Iraq would make the conflict worse. We know it would be civil war and the Demonrats know it would be civil war. They started making noise about 3 months ago that if they won the House and Senate that they would not do an immediate pull out of our troops. But, if they start pulling our troops anytime soon and there is a resultant mess, they will be blamed and they know it. What I see now is a lot of Democrats losing their seats in 08 irregardless of what they do about Iraq. If they do nothing they lose, if they proceed and the end result is a bloody mess and it will be they lose.
What they are hoping for now is that they can propose to exit Iraq, but not get it through Congress. Then assuming the war continues to go badly, they can use the fact that they tried to leave Iraq in the 2008 election without having to face up to the nasty consequences of a cut & run.
In the case of Iraq, we have a former slave class, the Shia, being attacked by the former slave-owning class, the Sunni Arabs, and it's really difficult to suggest that their only difference is one of political ambition.
The best solution is to send the Sunni Arabs back home.