President Obama ’s task of selling a potential nuclear agreement with Iran to a skeptical Congress became far harder on Tuesday after an impassioned speech by Prime Minister Benjamin Netanyahu of Israel to lawmakers already nervous about the deal. “The president has a very heavy burden of persuasion here,” said former Representative Lee H. Hamilton, a Democrat and the onetime chairman of the House Foreign Affairs Committee who now directs Indiana University’s Center on Congress. “That task is made much more difficult when a powerful case is stated against the emerging deal, as the prime minister has done.” Although Mr. Hamilton said he doubted many minds were changed by Mr. Netanyahu’s words, he said that “what a speech like this does is reinforces and intensifies the opposition at a critical point.” To be sure, others argued that Mr. Netanyahu’s address would have an effect opposite to the […]