Sen. Cotton (R-AR) first claimed that Constitution states that the Senate has to vote on any agreement with Iran in order for it to last, “It’s — well, as a simple fact that our Constitution that, if Congress doesn’t approve that deal, then it may not last.”
The Constitution says nothing of the sort. Via Article II Sec. 2, “He shall have Power, by and with the Advice and Consent of the Senate, to make Treaties, provided two-thirds of the Senators present concur; and he shall nominate, and by and with the Advice and Consent of the Senate, shall appoint Ambassadors, other public Ministers and Consuls, Judges of the supreme Court, and all other Officers of the United States, whose Appointments are not herein otherwise provided for, and which shall be established by Law: but the Congress may by Law vest the Appointment of such inferior Officers, as they think proper, in the President alone, in the Courts of Law, or in the Heads of Departments.”
The Constitution does not cover executive agreements like the one that is being negotiated with Iran. The president has the power to suspend the sanctions unilaterally, but that suspension would expire once he left office. It is true that the Senate may get to vote on the sanctions, but it is possible that if Democrats keep the White House, the next Democratic president will keep the sanctions suspended as long as Iran continues to comply with the agreement. Unless the president wants to go to Congress to ask for permanent removal of the sanctions, there is no guarantee that Congress will ever get a vote on the matter.