Reid, who is not seeking reelection in 2016, is now the 27th Senate Democrat publicly endorsing the deal. The two Democrats publicly opposing the deal are Sen. Robert Menendez from New Jersey and Sen. Chuck Schumer from New York, Reid's friend and likely successor.
"I'm going to do everything in my power to make sure the deal stands," Reid told The Washington Post.
"One of the most important national security challenges of our generation is stopping Iran from getting a nuclear weapon, a goal that is critical to the national security of the United States, the State of Israel and the world," Reid said in a statement. "I support this agreement because I believe it is the best path to stop Iran from obtaining a nuclear weapon."
The White House needs the support of at least 34 Senate Democrats to ensure the nuclear deal with Iran remains by preventing Congress from overriding Obama's potential presidential veto if Congress attempts to stop Obama from lifting U.S. sanctions placed on Iran.