The establishment consensus is hardening. President Trump’s war with Iran is the culminating disaster of the most damaging and misguided American foreign policy in history. Iranian leaders are humiliating the U.S., German Chancellor Friedrich Merz warned. “Superpower suicide” is how Wendy Sherman, a top Iran negotiator under President Obama and Joe Biden’s deputy secretary of state, described Mr. Trump’s Iran policy to ABC News. As Ms. Sherman sees it, the Iran war has alienated allies, assisted Russia financially, and weakened America’s position vis-à-vis China. For Fareed Zakaria, the question is no longer whether the administration’s policies will backfire but whether...