You may have noticed John McCain bringing up autism at the debate last night:
And, by the way, [Sarah Palin] also understands special-needs families. She understands that autism is on the rise, that we've got to find out what's causing it, and we've got to reach out to these families, and help them, and give them the help they need as they raise these very special needs children. [emphasis added]
At first glance, this might just seem like McCain is trying to turn Sarah Palin's experience raising a child with Down Syndrome into evidence that she is some sort of disability expert. However, it's a little more complicated than that.
Earlier this year, McCain waded into the fight over the cause of autism and expressed his apparent belief that autism could likely be caused by the mercury-based vaccine preservative thimerosal. This is among the latest in a long line of dubious claims of autism causation (earlier discredited theories have blamed excessive television watching and "emotionally distant mothers"), and doesn't have much in the way of evidence to back it up. Thimerosal hasn't even really been used in childhood vaccines since 2001, without any effect on the autism rate.
(It should be noted that Obama has had questionable views on the subject as well)
The main advocates of the thimerosal theory are a small but quite vocal minority of families of autistic children, and they generally don't take too kindly to people who question their pet explanation. So, best guess is that McCain probably didn't have much of a strong opinion on the issue, but took the opportunity to pander to an easily panderable group. I figured that was the end of it, but now that he's flogging that horse again it would be interesting to find out what his actual position is, and if last night's mention was deliberate or if he just picked some random developmental disorder that he could assert Palin has expertise on.
Also, this isn't just some gotcha moment to point out when someone doesn't know what the hell they're talking about (though it's that too). A belief that vaccines are dangerous for children will lead to people forgoing vaccination, turning what was just a kooky belief into an actual public health risk. Let's try to avoid a huge measles epidemic here, ok?