Presidential press secretary Jay Carney uttered 10 words the other day that represent a major presidential challenge to the American Israel lobby and its friends on Capitol Hill. Referring to Senate legislation designed to force President Obama to expand economic sanctions on Iran under conditions the president opposes, Mr. Carney said: “If it were to pass, the president would veto it.”

For years, there has been an assumption in Washington that you can’t buck the powerful Israel lobby, particularly the American Israel Public Affairs Committee, or AIPAC, ..