That should not come as a surprise to anyone familiar with the U.S. bipartisan consensus on Iran: For over 20 years, a number of prominent Democratic leaders — and in some cases, large majorities of congressional Democrats overall — have helped pave the groundwork for Trump’s war by issuing exaggerated and alarmist statements about Iran’s supposed danger to the region, threatening the use of military force, and undermining diplomatic initiatives, sometimes even criticizing Republicans from...