For the second time in a week, congressional Republicans have gone out of their way to try to undermine the Obama administration’s foreign policy.

As Bloomberg View’s Josh Rogin first reported on Monday, Senate Republicans released an open letter to Iran’s leaders rebuking the president’s efforts to negotiate a deal over the country’s nuclear program.

“It has come to our attention while observing your nuclear negotiations with our government that you may not fully understand our constitutional system,” the letter reads. It goes on to explain Congress’ role in the diplomatic process, and explain that the American president — unlike Congress — is limited to two four-year terms.

“What these two constitutional provisions mean is that we 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 warns. “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.”

In other words: Senate Republicans want Iran to think that President Obama is not a reliable negotiating partner, because he will not stay in office for the duration of a nuclear deal.

Fourty-seven senators signed the letter, which was organized by freshman senator Tom Cotton (R-AR). Only seven members of the Republican caucus declined to sign: Senators Lamar Alexander (R-TN), Susan Collins (R-ME), Thad Cochran (R-MS), Bob Corker (R-TN), Dan Coats (R-IN), Jeff Flake (R-AZ), Lisa Murkowksi (R-AK).

Ironically, as Harvard Law professor Jack Goldsmith points out, the Senate Republicans’ Schoolhouse Rock-style effort to educate Iran on the Constitution actually misstates the Senate’s role in the treaty process. Contrary to the letter’s claim, the Senate does not ratify treaties; instead, it gives its advice and consent to the president, who may then proceed with ratification.

Still, the letter’s broader point stands: Without Congress, any deal the White House strikes with Iran could be undone by a future Republican-led government. That said, the politics of scrapping a nuclear deal could be very complicated for the GOP — which helps to explain why the senators wrote a letter instead of holding a vote.

UPDATE: The Obama administration fired back at Senate Republicans on Monday afternoon.

“It’s somewhat ironic to see some members of Congress wanting to make common cause with the hardliners in Iran,” President Obama said, as quoted by USA Today.

White House Press Secretary Josh Earnest also denounced the senators’ letter, describing it as “the continuation of a partisan strategy to undermine the president’s ability to conduct foreign policy.”

Meanwhile, Iranian Foreign Minister Javad Zarif dismissed it as “mostly a propaganda ploy” — suggesting that he may understand American politics better than Cotton and his colleagues thought.

CORRECTION: Thad Cochran (R-MS) was one of the seven senators not to sign the letter, not Rob Portman (R-OH) as this article originally stated.

Photo: U.S. senator Tom Cotton of Arkansas speaking at the 2015 Conservative Political Action Conference (CPAC) in National Harbor, MD. (Gage Skidmore/Flickr)