Right, AdSense looks at the keywords on the site. But the other part of the equation is the advertisers who choose which keywords to push their ads on. So, if I wanted to associate "Mitt Romney" and "Mormon" in people's minds, I would bid my ads for "Mormon Ringtones" on the keywords "Mitt" and "Romney" and "Mitt Romney", thus ensuring appearance on those sites that mention him a lot.
So, you're thinking that there are companies out there blowing their ad budget to push the association of "Mormon" with "Mitt Romney?" Or, I don't know, maybe they're fictitious companies, created by political adversaries? It's not as if his religious affiliation isn't brought up with nearly every mention of his name already, in the MSM, so I have my doubts about that.
It strikes me as much more stratightforward to assume that these companies are merely trying to reach a Mormon audience, to sell their products expressly created for that audience.