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As the ebbs and flows of diplomacy with Iran once more fixate official Washington, a subtle shift is emerging in the Islamic Republic’s nuclear calculus. Officials in Tehran increasingly sense that it may be easier to get the bomb through an agreement than by pursuing it outside the parameters of a deal. But for this strategy to succeed, Iran has to get the right kind of an accord, one in which it trades size for transparency. Namely, the deal must allow Iran to construct an elaborate nuclear infrastructure in exchange for conceding to intrusive inspections. With the next round of talks looming, the challenge at hand is not just to negotiate an agreement with a disciplined adversary but to avoid the pitfalls of a flawed deal.