On a cold February day more than two decades ago, Ted Eubank, a dog breeder from Texas, stepped into the ring at the Westminster Kennel Club Dog Show for the first time. It was the first year that Cavalier King Charles spaniels — the silky-eared, saucer-eyed dogs that were Mr. Eubank’s specialty — had been allowed to compete in the prestigious dog show, which was then held at Madison Square Garden. The crowd around the ring was 10 people deep, he recalled recently.

“Talk about adrenaline, oh, my gosh,” he said.

In the years since, Mr. Eubank has become a seasoned Westminster competitor; his Cavaliers, including one indomitable champion named Rocky, have been named the best of their breed several times.

But on Monday, Mr. Eubank will be a rookie again when he makes his debut as a Westminster judge. He expects to feel a familiar flutter when he steps into the ring. “I will have butterflies,” he said.

More than 2,500 dogs — miniature pinschers, mastiffs and more — will compete in this year’s Westminster Dog Show, the second oldest consistently held sporting event in the United States. Westminster is a show for winners; only dogs who have racked up points at other competitions are eligible.

For a dog show judge, receiving an invitation to assess these canine champions is a prize of its own. “I felt like I won the lottery when the letter came,” said Michael Faulkner, of Center Cross, Va., who first judged at Westminster in 2001. “I actually cried.”

When Sharon Redmer, of Whitmore Lake, Mich., received her invitation, she was so excited that she “almost dropped the envelope,” she recalled. And Betty-Anne Stenmark, a judge in California, was not prepared when she was tapped to judge Best in Show in 2018. “I was sorry there was no champagne in the refrigerator,” she said.

Picking the best of the best is both a science and an art, Westminster judges said. The task requires applying exacting, rigorous (sometimes arbitrary-seeming) standards, but it also, in the end, often comes down to personal taste.

“We all see things differently,” said Cindy Vogels, who will be judging at Westminster for the ninth time this year. “That’s the beauty of it. And that’s what keeps people coming back.”

Purebred preparations

Westminster is what is known as a conformation show, and the job of a conformation judge is to assess how well a purebred dog exemplifies its breed: Is that curl-covered dog the Platonic ideal of a poodle? Does that golden retriever look like it can retrieve?

“You are looking at the dogs and trying to determine which dog gives you the signal that it could have done its original job description,” said Patricia Craige Trotter, who judged Best in Show in 2021. “What we’re doing is trying to achieve a level of near perfection in creating a working animal.”

Conformation judges must have a deep familiarity with the breed standards, which articulate the ideal version of each breed in exquisite detail, specifying everything including the desired pigmentation of the nose and the preferred facial expression.

In the United States, becoming an approved judge typically requires more than a decade of participating in dog shows, breeding and raising multiple litters of dogs, producing several champions, completing courses in canine anatomy, passing at least two tests and an interview and attending a judging institute, among other requirements.

“It’s harder to become a dog judge than a brain surgeon, to tell you the truth,” Mr. Faulkner said.

Some judges work just a few shows a year; others work more than 40, traveling to Europe, Asia and Australia for assignments. To earn a spot at Westminster, which sends out invitations as far as two years in advance, a judge must be established and experienced, said Donald Sturz, who judged Best in Show in 2022 and now serves as the president of the Westminster Kennel Club. A Best in Show assignment, in particular, is “the pinnacle for a dog show judge,” he said.

Judges might spend months preparing for Westminster. Mr. Eubank, who will judge eight breeds and varieties of toy dogs this year, has been reviewing the official breed standards, watching videos of judging at past shows and reconnecting with some of his mentors, who first helped him master the art of canine assessment.

Being a good judge also requires quick, clear analytical thinking, said Britt Jung, of Houston, who will be judging at Westminster for the first time this year. Ms. Jung, a former soccer player, feels a responsibility to be in top form for the dog owners and handlers who have expended so much effort to get to Westminster, so she is preparing for the event like an athlete.

“How would I prepare to be ready for a big game?” she said. “I eat well. I make sure I get good sleep. I make sure I stick to a routine.”

Canine prime time

When judgment day finally arrives, the occasion can feel momentous. The crowds at Westminster dwarf those at many dog shows. “You could just feel the electricity in the air when you walked out on the carpet to judge,” said Mrs. Vogels, who judged Best in Show in 2012.

A television audience raises the stakes. “You hope you don’t fall on your head or catch your heel on something and become famous for all the wrong reasons,” Mrs. Stenmark said.

But judges said their nerves calmed and the buzz of the crowd faded as soon as they started doing what they had trained for: sizing up dogs.

Because the dogs at Westminster are already seasoned champions, a Westminster title can come down to small details: the condition of the coat, the precision of the haircut or the synchrony between the dog and its handler as they move around the ring. “Was it just pure poetry in motion?” Mr. Faulkner said.

Often, it’s the more ineffable qualities that win the day. “It’s that little extra sparkle,” Mrs. Stenmark said. When she judged Best in Show in 2018, she selected the bichon frisé Flynn, a veritable canine cloud, as her winner. “This dog was asking for it,” she said. “Every time I looked at him, he walked out on the end of his lead and wagged his tail at me and cocked his head and said, ‘It will be me, right?’”

When Dr. Sturz judged Best in Show, he knew he’d found a winner when a bloodhound named Trumpet — who commanded the spotlight “in his own way, in a way that was befitting of a bloodhound” — gave him goose bumps, he said.

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.

For Mr. Faulkner, who is also an artist, judging dogs engages the creative parts of his brain. “I love the whole parts-to-whole gestalt approach to evaluating breeding stock,” he said. “And I love the balance and symmetry.”

And then, of course, there are the dogs. Although Mr. Eubank remains a Cavalier man, he adores all of the breeds he’ll be judging on Monday.

“I love pugs, I love min pins,” he said, referring to miniature pinschers. “I love Pekingese.”

Pomeranians? “They’re the cutest.”

Havanese? “Crazy about them,” he said. “I love them all.”