Two very smart sentences by Megan McArdle. She's talking about Walt & Mearsheimer's controversial book on the U.S. Israel lobby, but her point about affinity, not conspiricy, as the best, Ockhamesque explantion for most political behavior, is universal:

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.