WASHINGTON — In July 1975, just weeks before President Gerald Ford planned to travel to Helsinki, Finland, to wrap up more than three years of negotiations with European partners and the Soviet Union, Senate lawmakers moved to block what they believed to be a “one-sided agreement” favoring the Soviets. Like their anti-Iran counterparts in Congress today, legislators back then demanded that any deal reached in Helsinki be approved by both Houses of Congress before taking effect.

The Senate didn’t share the Ford administration’s vision of détente with the Soviets and had previously signaled its disapproval of the agreement under discussion in Helsinki, and sought to kill it. As one conservative Democratic senator put it on the eve of President Ford’s trip, “There are times in international diplomacy when the president of the United States ought to stay home.”

Despite the opposition, Mr. Ford defied lawmakers and flew to Helsinki, where he signed onto the Helsinki Final Act and achieved the first step in détente with the Soviets. Meanwhile, the Senate bill died a quiet death on the Senate floor.

History now looks kindly on Mr. Ford. Today the Helsinki accords are seen as one of the turning points in the long-simmering Cold War, leading to the eventual demise of the Soviet regime. In retrospect, President Ford and his administration are remembered for the accord they sought; their opponents are forgotten in the dustbin of history.

As Congress seeks to interject itself once more into delicate international negotiations — this time, with regard to Iran’s nuclear program — it is useful to consider how our world would be different had Mr. Ford and his secretary of state, Henry Kissinger, succumbed to the invective of outside analysts (the much-maligned Munich agreement between Nazi Germany, Britain, France and Italy was the historical epithet then as much as it remains now) and refused to pursue an agreement with the Soviet Union. What tragedy could have unfolded on the European Continent and how would American interests have been damaged in the process?

The world is better off for the courage of their convictions.

Consider, then, what will happen if Congress gets its way and sabotages a potential nuclear deal with Iran, ending the hopes for a peaceful resolution to the nuclear crisis and bringing us back to the brink of war.

As a possible nuclear deal emerges, Congress is moving to introduce legislation that would scuttle the best chance we have to win a nuclear agreement with Iran. Last week, Senator Bob Corker, Republican of Tennessee, and Senator Robert Menendez, Democrat of New Jersey, introduced a bill to set up a process whereby Congress would vote down any agreement and withdraw from the president his power to follow through on American commitments.

Just like their predecessors, they have wrapped their bill in high ideals, saying its purpose is to ensure that Congress protects its constitutional prerogatives in the making of international agreements and determines for itself whether any nuclear deal with Iran achieves American objectives.

But the senators’ justification also carries a false note. According to a report prepared for the Senate Foreign Relations Committee in 2001, more than 90 percent of all international agreements that the United States has struck since 1939 have been solely executive agreements. In other words, these senators have picked an opportunistic time to demonstrate their constitutional literalism.

The real motive underpinning the Corker-Menendez bill is to scuttle a nuclear deal by preventing President Obama from being able to carry out America’s pledge to suspend sanctions on Iran in the event of an agreement. This, along with the recent letter from Senate Republicans to Iran’s leadership that is intended to frighten Iran by hinting that the United States might later renege or reverse an agreement, could prevent Iran from signing a deal.

It is a perverse calculation, but not an unexpected one from a Congress so often ripe with rhetoric but devoid of constructive ideas. This isn’t a considered piece of legislation; it is a final warning shot to Iran from a Congress desperate to continue the brinkmanship that has defined the past decade.

As President Obama has learned but Congress has yet to figure out, there is no off-ramp to the nuclear crisis other than a negotiated solution that addresses the concerns of both parties. And this is why the president cannot entrust a nuclear agreement with Iran to the whims of Congress.

With a nuclear deal close at hand, President Obama has the chance — like President Ford and Mr. Kissinger before him — not just to resolve a nuclear crisis, but also to win for future generations a much-desired peace.

This piece originally appeared in the New York Times.