Jeffrey Goldberg in The New Yorker:
AIPAC is a leviathan among lobbies, as influential in its sphere as the National Rifle Association and the American Association of Retired Persons are in theirs, although it is, by comparison, much smaller. (AIPAC has about a hundred thousand members, the N.R.A. more than four million.) President Bush, speaking at the annual aipac conference in May of 2004, said, “You’ve always understood and warned against the evil ambition of terrorism and their networks. In a dangerous new century, your work is more vital than ever.” AIPAC is unique in the top tier of lobbies because its concerns are the economic health and security of a foreign nation, and because its members are drawn almost entirely from a single ethnic group.
More here.