The accord’s benefits far outweigh its costs. While the agreement will not prevent a determined Iran from building a nuclear weapon, it will make doing so much harder, and the extensive verification and inspection procedures will make it much easier to discover any such attempt. The easing of sanctions, and the ease with which they can be reimposed, provides a powerful incentive for Iran not to take that risk.

In addition to worrying allies abroad, the other problem with linking the nuclear accord to improved American-Iranian relations is the fact that ties may not get better, especially if Iran’s regional policies — like providing life support to Bashar al-Assad’s government in Syria and supporting terrorist organizations — become more aggressive.

No one knows if the nuclear agreement will be followed by a more moderate Iranian approach to Syria, Iraq and Lebanon. I suspect it won’t be, because the Revolutionary Guards remain at the core of the Supreme Leader’s coalition and they, not the moderate foreign minister, are the crucial advocates of an aggressive stance in the region. It’s far better to explain how the accord advances American national interests, whether or not Iran changes its regional policies.