On a basic level, the framework deal between world powers and Teheran will be judged by whether it prevents an Iranian nuclear bomb, but that will take years to figure out.

A more immediate issue is the projection of Western power. Supporters of the framework deal can argue that the United States and world powers extracted significant concessions from Iran, breaking a decadelong impasse and proving that diplomacy backed by tough sanctions can bring about positive change even in the Middle East.

But if, as critics contend, the agreement ends up projecting US weakness, it could embolden rogue states and extremists, making the region's vast array of challenges, from the Israeli-Palestinian conflict and the Syrian civil war to the fighting in Libya and Yemen, even more impervious to intervention.