Since everyone’s weighing in on the Obama dog, including the Friends of the Peruvian Hairless Dog Association, I thought I’d give my advice: a Sheltie. They’re the best dog breed, full stop. Extremely smart, quickly receptive to training, loyal, gentle with kids and other animals, mindbendingly adorable, and conveniently small if you live in a city, though they need to be walked and ideally run frequently. Because they’re small herding dogs, they’re protective without being aggressive and extremely attentive. I am personally a cat person, so I’m loyal to cat-friendly presidents like Clinton (quoth a libertarian friend: “the best thing about the Clinton administration was Socks”). But I don’t think you can do much better than a Sheltie.
Actually, that’s not entirely true: I love border collies, which are basically bigger, more energetic, smarter, crazier Shelties, but I can’t really see ever owning one if I didn’t live on a farm.