America’s relationship with Israel is difficult to discuss openly in the United States. In March, we published an article in the London Review of Books titled “The Israel Lobby,” based on a working paper which we posted on the faculty Web site at Harvard’s John F. Kennedy School of Government. Our goal was to break the taboo and to generate a candid discussion of U.S. support for Israel, because it has far-reaching consequences for Americans and others around the world. What followed was a barrage of responses—some constructive, some not.

Every year, the United States gives Israel a level of support that far exceeds what it provides to other states. Although Israel is now an industrial power with a per-capita GDP roughly equal to Spain’s or South Korea’s, it still receives about $3 billion in U.S. aid each year—that is, roughly $500 per Israeli citizen. Israel also gets a variety of other special deals and consistent diplomatic support. We believe that this generosity cannot be fully explained on either strategic or moral grounds. Israel may have been a strategic asset during the Cold War, but it is a strategic burden in the war on terror and the broader U.S. effort to deal with rogue states. The moral rationale for unconditional U.S. support is undermined by Israel’s treatment of the Palestinians and its unwillingness to offer them a viable state. We believe there is a strong moral case for Israel’s existence, but that existence is not at risk. Palestinian extremists and Iranian President Mahmoud Ahmadinejad may dream of wiping Israel “off the map,” but fortunately neither has the ability to make that dream a reality.

The “special relationship” with Israel, we argue, is due largely to the activities of the Israel lobby—a loose coalition...