I wrote last week about the unreasonableness of the Obama administration's position that members of Congress are somehow straying beyond their proper bounds when they make it harder for the president to negotiate whatever deal with Iran he thinks best. A letter from 47 Republican lawmakers, warning that the president doesn't have the power he claims, a document first reported on by Bloomberg View's Josh Rogin, was a silly stunt. But its silliness doesn't alter the underlying constitutional or historical analysis. The president is still mistaken.

The Democratic response to the letter, however, suggests quite a different dynamic — and a deeper problem with the White House strategy. In essence, the president's defenders have argued that the letter harms the prospects for negotiation. A deal to stop or slow Iran's march toward a functional nuclear weapon, we are told, is less likely.

This is implausible.

Let's strip away the partisan cast and study the problem as one of negotiation. The Obama administration presumably believes that the Tehran regime is a rational and reliable negotiating partner. Seeking to work out a deal would otherwise be irrational.

QuickTakeIran's Nuclear Program

The rational choice model of conflict holds that states, like other actors, understand and pursue their own interests. States can choose among competing goals, and weigh the costs and benefits of a path of action before proceeding. There is no point to negotiating with a state that does not behave this way. Therefore the administration necessarily believes that Iran's self-interest includes reaching an agreement. If Iran's self- interest is pushing it toward an agreement, why would the open letter from the U.S. opposition party alter the outcome?

Three reasons suggest themselves.

First, the administration might contend that the letter draws unnecessary attention to the political divide within the U.S. This attention, in turn, might have the effect of frightening Iran away from the table.

But if, as we are assuming, Tehran wants a deal, then it will hardly be frightened away because of the words of President Barack Obama's political opponents. There is little possibility that Iran is less than fully aware of about the state of political play in the U.S. The only way that Tehran could be misinformed is if the administration has assured the regime that it can overcome its domestic opposition. If this is the case, then the problem is that the administration has promised what in fact it cannot deliver. Assuming this isn't so — assuming, in other words, that the U.S. negotiators have made no effort to minimize or conceal the extent of domestic opposition — then the letter supplies no new information that would cause Iran to walk away from a deal.

Secondly, the White House might be concerned that the more radical elements in Tehran will seize on the Republican letter to sway waverers at home against whatever deal is presented — perhaps about negotiations at all. In other words, opposition in Iran might be so great that the Islamic Republic's negotiators will now walk away from the table.

But this is unpersuasive. It's true that radicals in and around the Iranian regime adamantly oppose President Hassan Rouhani's negotiation strategy. It's also true that the Assembly of Experts, charged with selecting the Islamic Republic's supreme leader, has selected a hard-liner as its new chairman. Nevertheless, if the negotiations are so unpopular in Iran that the Republican letter will tilt the balance, then it seems likely that the talks would collapse in any case. And if the Tehran regime has crawled so far out on the limb that so mildly uncomfortable a breeze will bring everything down, it no longer qualifies as a reliable negotiating partner, because its ability to deliver on whatever it promises turns out to be hazy at best.

Thirdly, the administration might believe that Iran is looking for an excuse to blow up the talks. The Republican letter, then, might provide the excuse. The trouble is, if Tehran wants the talks to fail, then it is not after all a reliable negotiating partner. The effort to reach a deal was always doomed.

Where then are we left? As I noted, the Republican letter does not seem to me a particularly wise way of displaying legislative displeasure with what the administration is doing. The administration, however, is also taking an indefensible position in its insistence on the freedom to work out a deal without congressional input or approval. As I explained last week, the freedom only exists when Congress allows it to exist. Often the House and Senate are content to leave foreign policy to the executive. When Congress does demand a role, however, it's merely doing what the Framers of the Constitution envisioned. That the senators who signed the letter may choose to display their unhappiness in ways that are combative, partisan and even self-indulgent doesn't mean they don't have a case.

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