“Dogs don't bark at parked cars.” If the dog is barking, the car must be in motion, but it is not necessarily what deserves the attention. If my reading is correct, the saying is distinctly different from “if there's smoke there's fire.” It's also contrary to A. Conan Doyle's the curious incident of the dog in the nighttime where the dog's not barking is significant. Here the bark is meaningless because you cannot trust the dog to pay attention to what is really going on; it is just responding to motion.

This one came to the attention of lexicographers because Lynne Cheney used it in an interview on MSNBC in explaining why her husband, Dick, is such a “lightning rod” in the Bush administration. Apparently it is because he gets things done.