When people move into the White House, they get a dog. Sometimes a cat too. Some of them actually had dogs before the White House, which is a different matter. It's about Pet Politics. (As you may recall, the Clinton's Lab was promptly run over by a car after leaving the WH, and Hillary dumped her famous cat on the secretary. I suspect the Bush's still have their dogs.)
The breed the Obamas decided to exploit is the Portuguese Water Dog. It's probably a breed ancestor of the Poodle. They need more daily exercise than any White House pet is likely to get.
I don't know how anybody can live without dogs around the place.