The American Prospect has a long article on "How Congress Helped End The Vietnam War" by Julian Zelizer. It gets to the parts most immediately relevant to the current Iraq situation about 2/3 of the way through:
In 1972, [Sen. Frank] Church [of Idaho] and Senator Clifford Case of New Jersey were able to push through the Senate an amendment to foreign-aid legislation that would end funding for all U.S. military operations in Southeast Asia except for withdrawal (subject to the release of all prisoners of war). Senate passage of the legislation, with the amendment, marked the first time that either chamber had passed a provision establishing a cutoff of funds for continuing the war. Though House and Senate conferees failed to reach an agreement on the measure, the support for the amendment was seen by the administration as another sign that antiwar forces were gaining strength. ………
During the final negotiations with the Vietnamese over ending the war, culminating with the 1972 Christmas Bombings and the Paris Peace Accords in January 1973, the president knew that he only had a limited amount of time before Congress finally used the power of the purse to bring the war to an end — regardless of what the administration wanted. Indeed, to make certain that the president could not reverse course, in June 1973 Congress passed legislation that included an amendment sponsored by Church and Case to prohibit the use of more funds in Southeast Asia after August 15. Sixty-four senators voted in favor. When the House assented, its vote marked the first time that chamber had agreed to cut off funds, too.
Take that, do-nothing Biden!
One of the interesting things this article doesn't get into, despite its length, is something that antiwar forces need to be stiff-spined about: that things were really, really superugly for quite a while there in Vietnam and Cambodia after the U.S. pulled out, as they are likely to be in Iraq–something admitted to by antiwarriors from both the left and libertarian sides in this piece by me from back in December.
That's something that antiwar politicians especially need to keep in the front of their mind, and be ready for. Indeed, such awareness, and an unwillingness to stand behind all the talk of "who lost Iraq?" going into an election year, may well play into whether or not anyone in Congress ultimately gets serious about saying no to George.