Twice recently, Iran’s president, Hassan Rouhani, has acted boldly in support of his biggest political gamble, pursuit of a nuclear agreement with the major powers. In a speech last Sunday on Iran’s troubled economy, he argued that Iran will never enjoy sustained growth if it is isolated from the rest of the world. Three weeks earlier, he made clear that he would confront Iran’s hard-liners in his efforts to clinch a deal in which Iran would agree never to produce a nuclear weapon in return for the lifting of crippling international sanctions. But Mr. Rouhani is not the only leader trying to keep a potential agreement from being savaged by domestic opponents. President Obama has a similar problem in Congress, where Senators Robert Menendez, a Democrat from New Jersey, and Mark Kirk, a Republican from Illinois, are expected to introduce legislation that could torpedo any deal by imposing new […]