Republicans have made no secret of their desire to sabotage multilateral negotiations over the Iranian government’s nuclear capabilities. That was the near-explicit purpose of Israeli Prime Minister Benjamin Netanyahu’s address to Congress last week. It’s what Senator Tom Cotton was getting at several weeks ago, when he said, “the end of these negotiations isn’t an unintended consequence of congressional action. It is very much an intended consequence.” And it’s supposedly the purpose of an open letter Cotton wrote—and that 47 Republicans signed—advising the Iranian government that the U.S. political system probably won’t sustain any deal they reach with the Obama administration.

“[W]e will consider any agreement regarding your nuclear-weapons program that is not approved by the Congress as nothing more than an executive agreement between President Obama and Ayatollah Khamenei,” the letter reads. “The next president could revoke such an executive agreement with the stroke of a pen and future Congresses could modify the terms of the agreement at any time.”

The hope, as Bloomberg’s Josh Rogin explained, is that “the Iranian regime might be convinced to think twice.” Put another way, Republicans want Iran to abandon negotiations and get to work on a bomb, thus inviting harsher measures. The administration and its allies in the non-proliferation community are predictably aghast, but their anger stems mostly from the Republican Party’s recklessness and its abandonment of political norms—which generally don’t include lobbying foreign governments to undermine a U.S. administration’s diplomatic undertaking.

In all the tut-tutting, though, I’ve yet to read a convincing case that Senate Republicans have advanced that goal even incrementally. The brazenness of their behavior has clouded the strategic question of whether this kind of intervention will actually have its intended effect. I don’t think it will. In fact, if you actually examine the incentive system the Obama administration is hoping to establish in a deal with Iran, it’s hard to escape the conclusion that Republicans have set back their own cause.

The letter itself is built on the presumption that Iranian negotiators don’t “fully understand our constitutional system.” That they’re unaware of the political obstacles any deal will face going forward, or that perhaps they’ve been misled into believing that Obama’s the only person in the U.S. government with any say over how a deal will play out.

In the first sentence of their missive, the signatories condescend to the people they’re trying to influence. That wouldn’t matter much if the GOP’s insights into the negotiations were correct, and the letter taught the Iranian government something it didn’t already know.

But the nature of the negotiations suggests the opposite. They are, after all, premised on the shared belief that the next administration won’t be as favorably disposed to diplomatic engagement, and thus that there’s some urgency to reach an agreement. More to the point, though, the deal that’s taking shape is built on the assumption that the U.S. Congress won’t lift sanctions on Iran, unless Iran submits to an intrusive inspection regime for years, to prove that it’s adhering to terms.

The two big threats to the viability of any agreement the Obama administration reaches with a foreign government is that a future (presumably Republican) president will undo it unilaterally, and that the U.S. Congress might reject terms that require changes to U.S. law. These negotiations reflect a recognition of both threats. If they produce an agreement, it will enlist the U.S. and its allies in an inspections regime that will be difficult for a future president—even a Republican president—to abandon unilaterally. And it will make sanctions relief contingent on Iranian compliance, such that a future Congress will be abetting the production of an Iranian nuclear weapon if it refuses to act.

A basic grasp of the U.S. constitutional system is thus baked into the theory of the deal. That moots the nominal purpose of the letter, which is actually a dramatic reminder that Obama is standing up to some powerful and motivated actors in the Republican party. A deal that ties one hand behind their back for at least two years, and then forces the other with a new set of facts, is probably the only way to circumvent them. The Obama administration wants Iran to believe it isn’t going to get a second bite at the apple. Senate Republicans just proved his point.