Recent conversations with senior Israeli officials are shot through with a sense of incredulity. They can’t understand what’s become of U.S. foreign policy.

They don’t know how to square Barack Obama’s promises with his policies. They fail to grasp how a president who pledged to work toward the abolition of nuclear weapons is pushing an accord with Tehran that guarantees their proliferation. They are astonished by the nonchalance with which the administration acquiesces in Iran’s regional power plays, or in al Qaeda’s gains...