The Democrats have tied themselves into knots over Iraq. First they let their fear of being perceived as weak force them into authorizing force. Then they let their fear of being held responsible force them into opposing the war. In order to explain this flip/flop, they were forced into an argument that they were deceived.
At no point in this process was the Democrat’s position dictated by the national interest or the facts on the ground. They have been playing the political expedient shots at each and every stage.
Now, the job for the Republicans is to make the case that Iraq is going to be a victory. This will force the Democrats to tack back, yet again, in order to claim credit for the success. This will be the bridge too far, and will destroy what little credibility the Democrats have left.