I think McCain is misinformed and was responding to a question from a parent with autism who really believes in this crap.
If he clarifies on the basis of sound science it will be a one day story. If not, as the folks at http://overlawyered.com note, he will have stepped in it big time:
"The Republican candidate sticks his foot in it in a major way on a topic extensively covered here over the years (as well as at my other site). Writes Mark Kleiman: "the thimerosal-autism theory is as dead as phlogiston in respectable company. I'm not surprised that 'respectable company' excludes a few ambulance-chasing lawyers looking for deep pockets and a some emotionally devastated parents looking for someone to blame. But it's distressing â€” to use no stronger term â€” that the presumptive Republican nominee for President, rather than looking at the evidence, has chosen to side with the panic-spreaders and pander to the emotions of the panic victims."
My take. This was a well-meaning but less than informed statement. McCain is not the first Senator to know little about the complexities of this issue. Let's give the guy a couple of days to actually look at the evidence instead of being force fed foolishness from Dan Burton.
And PS. Autism cases have NOT increase as the Senator stated. Reclassification explains the surge in incidence and prevalence.