Republicans stand by Iran letter, despite furor

By Patricia Zengerle WASHINGTON (Reuters) - U.S. Senator John McCain said on Thursday that Republicans stood behind a letter to Iran's leaders threatening to undo any nuclear deal despite an outpouring of criticism from the White House, U.S. allies and Democrats. "I certainly think I should have signed it, and I think that the message needs to be sent." The letter signed by 47 of the 54 Republican senators warned Iran that any nuclear deal made with President Barack Obama, a Democ