Via Kevin Drum I learn that Senator John McCain embraced unfounded anti-vaccination fears on the campaign trail. ABC's Jake Tapper reports:

At a town hall meeting Friday in Texas, Sen. John McCain, R-Ariz., declared that "there's strong evidence" that thimerosal, a mercury-based preservative that was once in many childhood vaccines, is responsible for the increased diagnoses of autism in the U.S. -- a position in stark contrast with the view of the medical establishment.

McCain was responding to a question from the mother of a boy with autism, who asked about a recent story that the U.S. Court of Federal Claims and the National Vaccine Injury Compensation Program had issued a judgment in favor of an unnamed child whose family claimed regressive encephalopathy and symptoms of autism were caused by thimerosal. . . .

"We've been waiting for years for kind of a responsible answer to this question, and are hoping that you can help us out there," the woman said.

McCain said, per ABC News' Bret Hovell, that "It's indisputable that (autism) is on the rise amongst children, the question is what's causing it. And we go back and forth and there's strong evidence that indicates that it's got to do with a preservative in vaccines."

McCain said there's "divided scientific opinion" on the matter, with "many on the other side that are credible scientists that are saying that's not the cause of it."

The established medical community is not as divided as McCain made it sound, however. Overwhelmingly the "credible scientists," at least as the government and the medical establishment so ordain them, side against McCain's view.

Moreover, those scientists and organizations fear that powerful people lending credence to the thimerosal theory could dissuade parents from getting their children immunized -- which in their view would lead to a very real health crisis.

Tapper does a good job of exposing the scientific illiteracy of McCain's remarks. Here's more from Orac and Mark Kleiman. Orac also has background on the court case referenced in the story. And my co-blogger David Bernstein blogged on media coverage of thimerosal here.