Bad science, shrewd politics?

It’s indisputable that autism is on the rise among 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. — Senator John McCain

And with that pronouncement, Senator John McCain touched one of the most politically controversial questions in modern medicine. He's right on the increase in diagnoses of autism. He's wrong on the alleged link between thimerosal and autism:

Several large-scale studies have found no evidence of a link between thimerosal and autism, and medical groups including the Centers for Disease Control and Prevention, the Institute of Medicine and the American Academy of Pediatrics have publicly stated as much. In January, California reported an increase in autism cases, despite the removal of thimerosal from most vaccines.

In February, an international team of researchers, analyzing blood samples from vaccinated children, found that blood levels of ethyl mercury “fell rapidly and had largely returned to baseline levels by Day 11 after vaccination.” Those levels fell much more rapidly, for instance, than levels of the mercury people absorb by eating fish — suggesting that the injected thimerosal is less likely to build up in the blood, the researchers concluded.

But because the parents who fervently believe that the government and vaccine provenders have somehow conspired to cripple their children trust none of the science, Senator McCain's comment on autism arguably represented shrewd politics.

This is not the first time that the Republican presidential campaign has encountered a politically contentious scientific issue. At a May 2007 debate, three candidates — Sam Brownback, Mike Huckabee, and Tom Tancredo — indicated that they did not believe in evolution:

The May 2007 debate	Mike Huckabee explains further

To his credit, Senator McCain did answer a simple yes when that question first arose.

Evolution denial has deep consequences for environmental policy. I'll go further: no person who denies the overwhelming scientific case for evolution has any business being President. As I write this, the last of the deniers in the Republican field is being eliminated — by Senator McCain, who has shown in an arguably less contentious context that he too can and will deny science when doing so confers a putative political advantage.

God save the United States.