John over at the Article 6 blog made it clear that McCain had two targets with Mosteller's attack on Romney: Romney himself, and the Evangelicals. He sought to taint Romney among the "values voters" by suggesting that he really doesn't have their values, and he sought to taint those same "values voters" in the eyes of the mainstream GOP by showing them as rednecked, ignorant bigots.
It was a brilliant "two-fer" move that would've worked perfectly in 1986. The problem is that time, tide, and technology wait for no man, not even an ambitious Senator looking to move to 1600 Pennsylvania Avenue in the Year of Our Lord Two Thousand Eight.
In The Age of Google, these kinds of slimy tricks are harder to pull off. As our ability to develop new forms of information from raw data evolves (such as the still-new and imperfect methods of social network analysis), it will get harder yet.
A few minutes of quality time with Google outed Mosteller as a McCain sock puppet. This might have been avoided by using a relative unknown--but getting such an unknown into place for this meeting would require sponsorship, and sponsorship is traceable.
Given enough planning and forethought, it might be possible to "cleanly" plant such a stinkbomb. But that's today. In 2008, it will be harder--because we'll be able to more completely map out a person's social network and its connectivity.