The showdown between Congress and the president this month around the funding for the Iraq war isn’t the first of its kind. We’ve been here before, and we need not walk blindly down rhetorical dead ends.

In 1970, well into the Vietnam War, Sen. Mark O. Hatfield, a Republican, and Sen. George McGovern, a Democrat, introduced legislation to cut off funding by a certain date in the future for U.S. combat operations in Vietnam. The invasion of Cambodia, and the widespread anti-war demonstrations that followed throughout the country, focused political attention on the McGovern-Hatfield legislation as a means to reverse President Nixon’s Vietnam policies. A mobilization of public opinion, with TV and radio ads and a focused lobbying campaign, backed this effort.

What lessons can be learned to inform our present debate?

1) Opposition must be genuinely bi-partisan. Republican senators such as Charles Goodell, Charles “Mac” Mathias, and others joined Hatfield. And powerful Democratic senators such as John Stennis and Henry Jackson were ardent supporters of President Nixon’s policies. This meant debate on the war policy did not immediately degenerate into predictable partisan rhetoric. That allowed for more focus and examination of actual policy alternatives. Judgments on war policy had more of a chance to transcend partisan allegiance than they do today. Opposition to President Bush’s Iraq policy, as well as support, has to become more principled than a simple litmus test of loyalty to either party.

2) It’s not about supporting our troops. The McGovern-Hatfield proposal established a date in the future – from nine months to a year in various versions – when congressional appropriations for U.S. combat troops in Vietnam would cease. In the meantime, it specified that all necessary support and funding for the troops be provided. No policymaker would ever propose that we stop buying bullets for soldiers that are deployed.

Today’s Iraq debate seems framed by arguments over who can best support our troops. The president and vice-president maintain that we must continue the war in order to support our troops. But that is a non-sensible rationale for a war policy. Democrats argue that we best support our troops by bringing them home. Likewise, that’s no foundation for reversing a war policy, only a consequence.

Supporting the troops is not the issue. That’s a given. The question is whether our Iraq policy is right or wrong.

President Nixon tried hard to frame those such as McGovern and Hatfield as not backing our soldiers in the field. He even argued that we must continue the Vietnam War in order to get our prisoners of war returned – as if that would not be a part of a negotiated end to the war. That’s why the protest of the Vietnam Veterans Against the War, where John Kerry entered the public spotlight, was the most threatening of any opposition to Nixon’s policies. Hippies could be dismissed, but not uniformed veterans.

3) It is about the money. Sen. Hatfield’s opening arguments on the Senate floor (this was at a time when speeches in the Senate actually seemed to matter), when he and George McGovern introduced their proposal, centered on Congress’ constitutional power of the purse regarding war. A long list of distinguished constitutional scholars agreed. Those arguments are being recycled today.

The president is right to say that Congress shouldn’t “micro-manage” the strategy and tactics of war. But that’s a clever rhetorical phrase that is largely meaningless. Congress does have the clear right to establish whether and when its support of a war, through its appropriations, will come to an end. Then it is up to the president and his military commanders to manage and implement that goal.

Other means of congressional opposition are largely empty rhetoric. Granted, the power of the purse is a blunt instrument for policymaking regarding war. But it is the constitutional avenue clearly provided, through which elected representatives can balance the power of the executive with the will of the people. Members of Congress who are convinced our Iraq war policy is wrong should not pay for it after an agreed and reasonable date. Those who believe it is right should write a blank check.

4) Political pressure eventually works. The McGovern-Hatfield amendment never passed the Senate. It first received 39 votes, then 42, and then, under the less politically volatile name of Sen. Lawton Chiles, 49 votes. Had McGovern-Hatfield passed and been adopted by the House, President Nixon would have vetoed it.

But all these congressional actions created a political environment that limited Nixon’s options. He began withdrawing troops and finally negotiated an end to the war. Despite their dire predictions of outcomes, today U.S. companies are racing to catch up with other corporations heavily investing in Vietnam’s economy.

In retrospect, we see now that successful congressional action could have ended the Vietnam War sooner, saving thousands of lives and achieving the same outcome. U.S. troops will be withdrawn, at some date, from Iraq. The question is when, and how. Congress can and should use its constitutional power to influence that outcome.

Rev. Wesley Granberg-Michaelson served as legislative assistant to Sen. Mark O. Hatfield from 1968 to 1976 and was his chief legislative strategist on Vietnam. Today he serves as general secretary of the Reformed Church in America.