A friend sends along this review of Walt and Mearsheimer which points out that it was not a very good book. And indeed it was not. But plenty of bad foreign policy books have been written before by famous people. Most of them committed the same error of vastly overstating the influence of whatever group they were describing. Few are as vilified as Walt and Mearsheimer, or as often facilely dismissed with insinuations of bigotry. I think that's a real problem. You cannot have a serious policy discussion if you are obliged to pretend that only one side has all the interest groups.
This is something that conservatives find maddening when liberals do it--pretending that Exxon is a lobby while Sierra Club is a bunch of rationally disinterested observers. I think that conservatives should appreciate that part of the contribution. On the other hand, the meat of Walt and Mearsheimer's argument does something that properly drives conservatives and libertarians nuts, which is to grotesquely oversimplify the way that lobbies work. I think they were out of their depth dealing with domestic lobbying, and simply projected their own understanding of IR onto domestic politics. But inter-state politics is very, very, very, very, very different from intra-state politics.
In some ways, the Israel lobby is more powerful than Walt and Mearsheimer posit, because like most muckrackers trying to expose the influence of powerful groups, they tend to assume conspiracy where affinity is a better explanation. Environmentalists excoriating the environmental lobby, for example, gloss over the fact that it is Detroit's union jobs, not its CEOs, that Michigan representatives labor so mightily to protect--that votes are usually a better explanation for politician behavior than campaign contributions. Similarly, Walt and Mearsheimer are prone to overestimate the Israel lobby's ability to snap its fingers and get its way, and vastly underestimate the public choice reasons for its success, much less the simple possibility that they consistently win because many Americans strongly agree that they should.
The problem is that W&M's critics often bypass useful criticism of their work, and try to put everything they say into the "lunatic conspiracy theorist" box. The accusation that someone secretly believes in an international Jewish conspiracy is nearly uniquely powerful in American culture, and merely hinting at it ends an argument.
Now, Walt's thought experiment may not be a good one, and I'm sure we could have a rousing argument about what a perfectly just counterfactual would be. But Ross didn't raise any of those issues. His retort is, simply, that Walt thinks there's an Israel lobby, and his book isn't very good. Both things are true. But they don't make Walt's questions any less useful, or urgent.