The Republican senator who gained infamy last year by attempting to sabotage a historic nuclear deal with Iran is back at it again   this time by trying to derail a crucial appropriations bill so America is forced to violate the agreement.Arkansas Sen. Tom Cotton got the moniker  Tehran Tom  after he and many of his Republican colleagues in the senate sent a brazenly out of line letter directly to the Iranian capitol in an effort to convince the country to stop negotiating with President Obama. The plan not only backfired (the Iranians delighted in mocking the Republicans), but it led to a major backlash from across the country. Politics may be getting nasty, but it seems betraying your country to score a cheap shot against the president still crosses a major line.Unable to understand when he has lost, Cotton has since been working behind the scenes to undermine the agreement any way he can. This week, he and his loyal band of obstructionists introduced an amendment intentionally meant to rankle relations between the two countries. Cotton had tried to bar the purchase of  heavy water produced in Iran.  Heavy water is  a component of making nuclear weapons and nuclear energy.  Part of the deal with Iran involved the country handing over its stock of heavy water (to show they were serious about ending their nuclear program)   but Cotton doesn t want America to take it. Why? Because then the deal would actually work.Needless to say, the White House was furious. At a press conference, Press Secretary Josh Earnest let Cotton have it: So it is clear what the intent of his amendment is. Senator Cotton is certainly no expert when it comes to heavy water. I m confident that he couldn t differentiate heavy water from sparkling water. His focus is on undermining the effective implementation of this agreement that prevents Iran from obtaining a nuclear weapon. Cotton is fast becoming a single-issue politician. The time and energy he pours into trying to hurt Iran-United States relation borders on pathological. Even many of his colleagues, some of whom signed his letter in 2015, have given up thinking they can stop this agreement. Not Tehran Tom. He keeps plugging away.On Twitter, Cotton did not take the news of his White House dress down well. He suggested that he, a sitting United States Senator, isn t aware the existence of  sparkling water  because he was in the military   a claim many found  dubious.As for you @PressSec , you re right, I don t know much about sparkling water. It isn t served in Army, unlike in your ritzy West Wing.  Tom Cotton (@SenTomCotton) April 27, 2016Maybe Cotton can get some of his lobbyist friends to send him a few bottles.Featured image via Mark Wilson/Getty Images