The question for the world, and especially for the Obama Administration, is whether those dire consequences are worse than the risks of a pre-emptive strike. We think we know what the Israelis will decide, especially if they conclude that President Obama stays on his current course.
Opponents of a pre-emptive strike say it would do no more than delay Iran's programs by a few years. But something similar was said after Israel's strike on Iraq's Osirak reactor in 1981, without which the U.S. could never have stood up to Saddam after his invasion of Kuwait. In life as in politics, nothing is forever. But a strike that sets Iran's nuclear programs back by several years at least offers the opportunity for Iran's democratic forces to topple the regime without risking a wider conflagration.
No U.S. President could undertake a strike on Iran except as a last resort, and Mr. Obama can fairly say that he has given every resort short of war an honest try. At the same time, no U.S. President should leave his successor with the catastrophe that would be a nuclear Iran. A nuclear Iran on Mr. Obama's watch would be fatal to more than his legacy.