Lots of people are talking about John McCain's lunatic pronouncement that "there’s strong evidence" for the proposition that thimerosol, a mercury-based preservative used in vaccines, causes autism. This is nonsense on stilts. While it might once have been a viable theory, there is now multi-national evidence that removing thimerosol from vaccines (as the US did in 2001) causes no decline in the rate of autism. Why, people ask wonderingly, is the good senator wandering around claiming otherwise?

I offer two explanations, neither of them mutually exclusive:

1. The desperate parents who believe that thimerosol caused their child's autism are highly motivated people with a very good chance of voting for anyone who says he believes them. The researchers who study thimerosol probably weren't going to vote for McCain anyway. No one else votes on the issue.

2. The vast expansion of the state means that we expect our representatives to have opinions on everything from missile defense to flame-retardant pajamas. No one could possibly learn about every subject we expect them to know, even if he were not spending sixteen hours a day doing the grip-and-grin with voters, lobbyists, donors, and other politicians.

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