Consider this hypothetical scenario. The Iranian parliament, the Majles, assembles and hardliners begin railing against the country's chief nuclear negotiator, Mohammed Javad Zarif. They call for a vote of impeachment and the measure narrowly passes. Nuclear negotiations with the U.S. are thrown into chaos. Many Iranian MPs, clerics, and newspapers gleefully claim the talks no longer have legitimacy.

As evidence for the vote of impeachment, the hardliners' Exhibit A is the letter sent to Iran's leaders, drafted by Senator Tom Cotton, and signed by Senator Rand Paul.

After all, the conservatives reason, why should we place any more faith in Zarif? Didn't America just admit the negotiations are a charade, to be canceled on a whim by the next president?

Could this happen? Fortunately it isn't likely, but there is significant precedent. Last year, hardliners in the Majles tossed out Iran's science minister, who they felt was doing too much to liberalize the country's universities.