As Republicans celebrated the death of Iran’s supreme leader, Ayatollah Ali Khamenei, with praise for Donald Trump’s decisive action, Democrats faced their own divisions and a reckoning over how to present a united front. Most were quick to condemn the US president for sidelining Congress to launch an illegal and unconstitutional war and demanded a swift vote on a war powers resolution that would restrain his military onslaught. But some in the party also felt obliged to acknowledge the authoritarian Khamenei’s death as a positive development and demonstrate their support for US troops. A small band of centrist Democrats have...