Iran’s Quds Force, which the Biden White House has reportedly discussed removing from the terrorism list, has more than a hundred active agents operating inside the United States, according to former U.S. and Iranian intelligence officials. Their current goal is to penetrate the security perimeter surrounding former President Donald J. Trump and to kill him. The Iranian plot is not a secret: Iran’s Supreme Leader, Ayatollah Ali Khamene’I, boasted in January that Iranian agents inside the United States were tracking the former president’s movements, and could penetrate the security systems protecting him. That boast appeared in the form of a...