On another night, a different dog might have risen to the top. “You know how great athletes can have an off night? Well, so can great animals,” Mrs. Trotter said.

Although the breed standards provide blueprints, judges have their own preferences and priorities. For some judges, Mr. Eubank said, judging a Cavalier King Charles spaniel is primarily about finding a pretty face. (The breed standard calls for a “sweet, gentle, melting expression.”) But for Mr. Eubank, who grew up with uber-athletic sporting dogs, a winning Cavalier must also move beautifully around the ring.

The audience, which can be boisterous at Westminster, often has preferences of its own. But if there is wisdom in the crowd, it cannot be trusted by a conformation judge. Audience members “just glom on to something, and they like it,” Mrs. Vogels said. “They don’t have the expertise to know whether it’s great or not.”

Dog show judging has its downsides. The travel can be grueling. Dog bites are an occupational hazard. And where there are winners, there are sometimes sore losers. “You’re brilliant if the dog wins, and you’re an idiot if the dog doesn’t,” Mrs. Stenmark said.

Still, judges said they couldn’t imagine giving up the pursuit, which they are drawn to for a variety of reasons. “I guess it’s my drug of choice,” said Mrs. Stenmark, who said she got “a thrill” when she saw a superlative new dog step into the ring.