Peter Feaver of Duke University, who has long studied public opinion about war and worked in the administration of President George W. Bush, said the Obama administration’s policy was now “in the exact middle of American public opinion on Iran” — taking a hard line against a nuclear-armed Iran, yet opposing military action for now and escalating sanctions. But as the November election approaches, Mr. Feaver said, inflammatory oratory is likely to increase, even if it is unsuited to a problem as complicated as Iran’s nuclear ambitions. “This is the standard danger of talking about foreign policy crises in a campaign,” he said. “If you try to explain a complex position, you sound hopelessly vague.”