Sen. Rand Paul

(Olivier Douliery/Abaca Press/TNS)

An open letter to the 47 U.S. senators who signed a letter addressed to Iran’s political leaders:

We are struck by your letter that condescendingly attempts to lecture Iran’s leadership on the fine points of the U.S. Constitution while at the same time blatantly trampled on the constitutionally defined roles in foreign affairs of presidents and members of Congress. In short, the chief executive negotiates and the Senate ratifies, or not, as the case may be.

Yet, your letter is a clear attempt to preemptively wreck the president’s attempts at a settlement to put Iran’s nuclear ambitions in check. And this provocative letter is well beyond the protocol for how the U.S. government negotiates international treaties.

The nation works best when its rival political factions present a united front to the wider world. “Politics stop at the water’s edge” might be an old cliche, but it has served us well.

There is a route for a politician to take on a bigger role in foreign affairs, one wholly endorsed by the Constitution. One of you 47 senators could win the presidency.

In fact, several of you who signed the letter harbor presidential ambitions, particularly Sens. Rand Paul, R-Ky., Marco Rubio, R-Fla., and Ted Cruz, R-Texas. How would a future administration of President Cruz or President Rubio or President Paul view a group of future senators so directly and maliciously involving themselves at the negotiation table? Not very well, obviously.

Perhaps, though, the letter isn’t really intended for Iranian eyes. Perhaps your real audience is domestic, political allies steadfastly opposed to anything President Barack Obama attempts. After all, the political affiliation of the signers is unmistakable — 47 Republicans (including Alabama’s Richard Shelby and Jeff Sessions) and zero Democrats. Thus, the message of this letter is a reminder to like-minded constituents: We matter.

The rest of your colleagues matter, as well. Now would be a good time to consider why none of them — seven Republicans and the rest Democrats, refused to attach their name to the letter. We can rightly assume it’s not because they are offering a blanket endorsement of any deal with Iran. Sen. Susan Collins, R-Maine, told reporters why she refused to sign. “It’s more appropriate for members of the Senate to give advice to the president, to Secretary [of State John] Kerry and to the negotiators.”

Our advice is to heed the advice of your colleague from Maine.