And yet, if this deal is not reached, the Republican-controlled U.S. Congress will punish the White House, and Iran, by imposing additional sanctions on Tehran. Obama, a Democrat, has said he will oppose those sanctions with a presidential veto but that does not mean the Congress cannot override his veto; they may.
Moreover, as dozens of senators reminded Tehran in a letter sent to the Iranian government last month, any agreement signed this year may not last longer than the duration of the Obama administration.