Republican Sen. Tom Cotton hasn’t been frog-marched from the Russell Senate Office Building — yet.

To believe the Arkansan’s harshest critics, that’s only because felonious traitors don’t get the punishment they deserve.

Cotton wrote an open letter to the leaders of Iran pointing out true and obvious things about our constitutional system, and the world came crashing down on his head.

Disgracing the Senate, per a hyperventilating Vice President Joe Biden, was the least of his supposed offenses. He was aiding Iranian hard-liners, violating the Logan Act against subverting US foreign policy and committing an act of treason.

If there were any doubt about the latter, the Daily News ran a picture of him and fellow Republican letter-signers with the subtle headline “TRAITORS.”

Cotton’s alleged sedition is hard to fathom. It’s not as though he wrote secret letters to the Iranians (that’s what President Obama has made a practice of doing).

It’s not as though he traveled to a foreign country to glad-hand a foreign thug in an express effort to undermine the president’s foreign policy (that’s what then-Speaker Nancy Pelosi did when she went to Damascus and met with Bashar Assad).

Cotton wrote a letter and posted it on his website. As The New Republic’s Brian Beutler pointed out, the letter is functionally indistinguishable from an op-ed.

It’s a trope among Cotton’s critics that he is allying himself with Iran’s hard-liners.

This is a hilarious plaint after Obama went out of his way in 2009 to say nothing when the Iranian regime was crushing the country’s true moderates, out in the streets in the short-lived Green Revolution.

It is Obama who has been wooing the most powerful hard-liner in Iran, unless we are supposed to believe that Ayatollah Khamenei is now a moderate.

The contents of Cotton’s letter shouldn’t have been news to anyone.

If the mullahs weren’t already aware that there is bipartisan opposition in Congress to any likely deal and the agreement won’t have the force of a treaty, they need to watch more C-SPAN and read up on the US Constitution.

It is inarguable that, as a matter of domestic law, a subsequent president can get out of the agreement at will and Congress can pass laws in contravention of the agreement, if a president will sign them.

If these are things the Iranians don’t know, and John Kerry hasn’t let them in on the joke, shouldn’t someone tell them?

The foreign-policy debate in the Age of Obama is the world turned upside down.

In the president’s transposition of the norms of American foreign policy, inviting the leader of a close ally to address Congress is an affront, and forging a — to put it gently — highly generous deal with an enemy is such an urgent necessity that no one should say a discouraging word.

A more confident administration would have brushed off Speaker John Boehner’s invitation to Bibi Netanyahu, as well as the Cotton letter. The Obama administration is so defensive because it has a lot to be defensive about.

It has been outnegotiated by the Iranians. Once, we wanted to prevent Iran from having a nuclear-weapons capability.

Once, we wanted zero enrichment, and so did the United Nations. Those goals have long since been abandoned by an Obama administration desperate for any deal so it can include an opening to Iran among the president’s legacy achievements.

So, here’s my own seditious foray into interfering with the conduct of US foreign policy:

To Whom It May Concern in Tehran,

You’re unlikely to ever encounter someone this weak and credulous again in the Oval Office.

The president used to say that no deal is better than a bad deal. Now, that line is inoperative. It’s any deal is better than no deal, and woe to anyone who dares say otherwise.