The dog, officially named Ch. Clussexx Three D. Grinchy Glee, is the first Sussex spaniel to win the top prize at Westminster, The New York Times reported, although the breed was among the first to be recognized by the American Kennel Club.
"I didn't know who he was or how old he was," Judge Sari Brewster Tietjen said after the show Tuesday. "He's just everything that you'd want in the breed, and I couldn't say no to him."
Other dogs competing in Best in Show were a standard poodle, a Scottish terrier, a puli, a Brussels griffon and a Scottish deerhound.
Stump won the sporting group at Westminster in 2004, but in early 2005 became seriously ill, only fully returning to form last year, said Scott Sommer, the dog's handler and an owner along with Cecilia Ruggles and Beth Dowd.
Stump's win ended the reign of Uno, the beagle who achieved canine celebrity status in 2008 after becoming the first of his breed to win Best in Show.