[This is the first ever guest post on Math Of Politics. If you’re interested in posting on Math Of Politics, drop me an email.]
To understand the Cotton letter, we need to think about the operation of treaties. Treaties are like contracts, designed to solidify current behaviors or constrain future behaviors for some period of time. Treaties fail when the prescribed behaviors are no longer individually rational for at least one of the parties to maintain. Failures can occur almost instantly – consider some of the recent treaties regarding Ukraine. Alternatively, treaties can teeter on the verge of failure (or success) for quite some time. Of course, individual rationality is best understood in the eyes of the beholders, and holders of political office come and go (as Cotton reminded everyone). Is political succession problematic for treaties? Elections are known, but who will win the next presidential election is unknown. In the words of a former defense secretary, these are known unknowns. But there are also unknown unknowns. What the hell is happening in this world? Summing up, some exogenous shocks are more exogenous than others. Treaties are not automatically vulnerable (or invulnerable) to exogenous shocks, but it is easier to brace for the known unknowns than the unknown unknowns.
So, why did Cotton remind the Iranian leaders that the U.S. has regular elections and that treaties can fail?
Ostensibly, Cotton was worried about the sort of treaty being negotiated. To what type of treaty will leaders submit? A desperate leader might agree to a treaty with very little lasting power. Consider 24 or 48-hour ceasefires. Does the success or failure of Obama’s last two years depend on securing any sort of agreement with Iran? I think it’s reasonable to suggest that Obama secures few immediate brownie points for his negotiations with Iran, so the possibility of long-term gains likely play the dominant role. But if Obama is not focused on short-term political gains, he needs a treaty with some lasting power.
Of course, a treaty with lasting power must be somewhat invulnerable to regular electoral shocks – our known unknowns. To think that Obama would agree to a treaty that will be undone as soon as he leaves office is to suggest that Obama has only short-term gains in mind. Long-term gains would be impossible because political succession would ensure the renegotiation and demise of Obama’s treaty. Unless presidents cannot imagine the world after they leave office, some subgame calculations seem warranted. My guess is that the president and the Iranian leaders were both comfortable assessing the implications of elections and other known unknowns.
So, why did Cotton write the letter? I can see two possibilities.
Possibility 1. Cotton et al. truly do presume that the Iranian leaders are unaware of the role of executive agreements in U.S. international affairs. This is possible, but unlikely. Newcomers to chess might like to think “he won’t see this,” but chess is a game of complete information. Everything is upright, literally above board. Similarly, executive agreements do not hide in the nether reaches of constitutional authority.
Possibility 2. Cotton et al. do believe that Iranian leaders are aware of the role of executive agreements. Cotton simply wants to emphasize that any agreement would be tied to a particular Democratic president and not a succeeding president. This could make sense if Cotton were to believe that the negotiators are not employing subgame perfection. Suppose Cotton does manage to convince the Iranian leadership that the agreement is designed for failure. If Cotton were convincing, the Iranians could heavily discount long-term costs and implications. Reluctant or hardline Iranians might be more willing to accede to a treaty that is projected by the political cognoscente to collapse in two years. Agreeing to a ten-year treaty is trickier. Thanks, Senator Cotton.
In the end, perhaps Cotton et al. did not use any subgame thinking of their own. That is, the authors of this infamous letter are complaining about a path of the game tree, but they are unaware that the offending path is well removed from the equilibrium path. It is reasonable to consider and debate possible equilibrium paths. Different equilibria typically treat parties very differently. Not all equilibria are worthy of our support. But to debate something off the equilibrium path seems to be a waste of everyone’s time – unless it is meant for crass political consumption. That the Iranian leadership failed to bite is telling. That 47 senators are still running a “Nobama” campaign is also telling. That a newly minted senator can secure 46 Republican signatures for a letter of questionable value bodes ill for the Grand Ol’ Party. There are few gains from debating the merits of non-equilibrium paths.
With that, I leave you with this.
 By some measures, negotiations with Iran have been ongoing for over a decade.
 The Iranians, who have their own concerns about political succession, are also likely focusing on long-term gains.
 As an analogy, consider a bank note. Suppose a large 30-year bank loan is problematic for a borrower. If mysteriously the bank were to dissolve with 50% likelihood after two years, the borrower’s long-term situation is less problematic. If mysteriously the bank itself were to dissolve entirely, the borrower’s situation is not problematic at all.
 This is not the time to consider trembling hand perfection or other equilibrium refinements that might allow one to imagine being off the equilibrium path.