Sen. Lindsey O. Graham (R-S.C.) speaks to reporters. (J. Scott Applewhite/AP)

Appearing on “Face the Nation” on Sunday, Sen. Lindsey O. Graham (R-S.C.)  had this exchange with moderator Margaret Brennan:

BRENNAN: If President Trump can pull off a diplomatic agreement with North Korea, does he need congressional consent for a treaty?

GRAHAM: I would urge the president if he can negotiate an agreement with Kim Jong Un that he takes that agreement and sends it to the Senate. I think that would be a good thing to do. This is a historic opportunity. But if the past is any indication of the future, you’ve got to watch North Korea like a hawk. But I do believe they’re at the table because they see a different person in Donald Trump. And they believe if he had to Trump would use military force. China certainly believes that.

Republicans, who complained vociferously that the Joint Comprehensive Plan of Action should have been put before the Senate as a treaty, would be hard-pressed to justify not demanding the same for any agreement reached with North Korea. The knowledge that two-thirds of the Senate would need to ratify it would act as a restraint on a president overeager to reach a deal that he can label as historic. (Sound familiar?)

Given Trump’s recent fawning over Kim Jong Un (whom he called “honorable” in his dealings and praised for “a very smart and gracious gesture” in dismantling a nuclear test site), there is ample reason to worry that the president will say whatever he feels necessary in the moment to come out with a “win.” Having the Senate as a backstop — with the ability to unwind rash decisions — would give the United States an added measure of security.

Moreover, the experience of the JCPOA, whatever the merits of the deal, is not one we should want to repeat. Without Senate approval, an executive agreement inevitably is riven by partisanship. The instability of such an arrangement and the potential for it to be undone, just as occurred with the Iran deal, makes the United States appear less credible both to friends and foes. Our allies who negotiated with us on the Iran deal are understandably angry — even if they went into the deal knowing it did not have the status of a treaty. (Frankly, they could be forgiven for thinking that a subsequent president and Congress would be unlikely to upset international arrangements, especially when the other party is in compliance.)

In Federalist No. 75, Alexander Hamilton warned about putting the sole power to forge international agreements in the hands of the president: “An avaricious man might be tempted to betray the interests of the state to the acquisition of wealth. An ambitious man might make his own aggrandizement, by the aid of a foreign power, the price of his treachery to his constituents. The history of human conduct does not warrant that exalted opinion of human virtue which would make it wise in a nation to commit interests of so delicate and momentous a kind, as those which concern its intercourse with the rest of the world, to the sole disposal of a magistrate created and circumstanced as would be a President of the United States.” There is a reason the Founding Fathers saw fit to make international agreements one arena in which two branches must act cooperatively.

And finally, from Trump’s selfish point of view, if he is able to come back with a stupendous deal that truly does denuclearize North Korea, he would not need to fear the Senate’s rebuke. He would have the satisfaction of knowing that unlike the JCPOA, his successor could not undo his handiwork.

In sum, it would behoove the Senate to speak with one voice now, before Trump meets with Kim in June 12. Having a firm understanding that any deal Trump reaches would be subject to Senate approval would give the Trump team both leverage and discipline, two things it badly needs heading into a high-stakes summit.