Here's an article by Robert Reich on the logic and political maneuvering by the Democrats of a) opposing the "surge" but b) continuing to fund it:

Why Dems Won't Stop Bush's "Surge" in Iraq

Bush will announce next week he wants 20,000 additional troops in Iraq. Most congressional Dems say they’re opposed, and they’ll use the upcoming confirmation hearings for Bush’s nominees to the United Nations and for Deputy Secretary of State to make their case. But Dems will still appropriate the extra money the "surge" requires. This is politically wise, although dreadfully cynical.

....As long as Dems remain opposed to Bush’s policies and the Democratic leadership offers some semblance of unity in opposition – while at the same time giving Bush the money he wants to carry out his policies – the Dem candidate in 2008 can blame Bush and the Republicans, and no Republican candidate who supports Bush will have a comeback. McCain’s strategy of distancing himself from Bush by arguing for more troops is about to backfire on him, because he’s going to get what he wants – and America will see just how tragically wrong he is (Edwards has already, adeptly, labeled it the "McCain doctrine."
Robert Reich website and blog: Robert Reich's Blog: Why Dems Won't Stop Bush's "Surge" in Iraq