argue, with a straight-face mind you, the Congress has a constitutional obligation to block the President's troop surge in Iraq. Not merely the constitutional power to block it, (which probably doesn't exist either) but an obligation to block the surge.
Whether you favor it or not Senator, under the Constitution, the President is the Commander-in-Chief-- not you wanna-be president guys and gals in Congress. You don't get to set national security policy, manage wars or choose a course of action. Therefore, you have precisely two options: 1) cease to fund the war, or 2) STFU and color.