P. G. Wodehouse wrote that the best way to discover a man’s character is to play golf with him. In his short story “Ordeal by Golf,” the narrator declares, “In no other walk of life does the cloven hoof so quickly display itself.” Donald Trump is an avid golfer, of course, as well as the avid proprietor of seventeen golf courses on both sides of the Atlantic. Indeed, all evidence suggests that he is far more interested in golf than he is in immersing himself in the duties of the Presidency. According to the Web site TrumpGolfCount.com , which meticulously tracks Trump’s play, he has made a hundred and sixty-five visits to golf clubs since becoming President, and he has played golf at least seventy-seven times. In March alone, he played six rounds at the Trump International Golf Club in West Palm Beach. Even when he is confined to Washington, he caters to his golf habit. The Washington Post reported that Trump had installed a state-of-the-art golf simulator in the White House’s living quarters, which allows him to pretend he is playing famous courses around the world.

By the standards of most weekend golfers, Trump is a decent player , as his playing partners attest, with a roundhouse swing that propels the ball a long way. But he doesn’t claim to be decent player; he claims to be an élite amateur who has won a remarkable eighteen club championships. (At any golf club, the club championship is the biggest tournament of the year.) Over the years, however, tales of Trump’s chronic cheating on the links have circulated widely. In the new book “ Commander in Cheat: How Golf Explains Donald Trump ,” the sportswriter Rick Reilly has pulled these stories together and found some new ones. Relying on testimony from playing partners, caddies, and former Trump employees, Reilly pokes more holes in Trump’s claims than there are sand traps on all of his courses combined. It is by turns amusing and alarming. “Trump doesn’t just cheat at golf,” Reilly notes. “He cheats like a three-card Monte dealer. He throws it, boots it, and moves it. He lies about his lies. He fudges and foozles and fluffs.”

Reilly recounts a time when Trump was declared the senior club champion at Trump National Bedminster, in New Jersey, even though he was in Pennsylvania on the day that the event was played. “He’d declared that the club should start having senior club championships for those 50 and up, but he forgot that one of the best players at the club had just turned 50,” Reilly writes. “Having zero chance of beating the guy, he went up to his Trump Philadelphia course on the day of the tournament and played with a friend there. Afterward, according to a source inside the Bedminster club, he called the Bedminster pro shop and announced he’d shot 73 and should be declared the winner. The pro, wanting to stay employed, agreed. His name went up on the plaque.”

This turned out to be a double con. When someone from the Bedminster club called up Trump’s caddy at the course in Philadelphia and asked what he’d shot there, the caddy replied, “Maybe 82. And that might be generous.”

Evidently, Trump pulls this kind of stuff on a regular basis. Last month, another well-known sportswriter, Michael Bamberger, reported that Trump won the 2018 club championship at his West Palm Beach club without playing in that tournament, either. And Trump admitted to Reilly that at least some of those eighteen club championships weren’t championships at all. “Whenever I open a new golf course, I play the official opening round and then I just call that the first club championship,” Reilly recounts Trump as saying. “There you go! I’m the first club champion!"

Trump’s other big golf brag is that he sports a handicap of 2.8. Handicaps are designed to rank players and to make it easier for weak players to compete against strong ones. A handicap of 2.8 indicates that a player is capable of playing a round in about three over par, which is extremely difficult to do. According to the United States Golf Association, Trump’s mark would put him in the top five per cent of players who keep a handicap. But these figures apply to players of all ages, and Trump is now seventy-two years old.

Among golfing septuagenarians, a handicap of 2.8 is very rare. Jack Nicklaus, who is either the best or second best golfer ever, depending on how you rank Tiger Woods, has a handicap of 5.2. If Nicklaus played Trump in a proper match, Trump would have to give him two shots. The Golden Bear is seven years older than Trump, but, as Reilly asks, “If you needed a partner for a death match . . . would you take Trump or Jack Nicklaus?”

Actually, it might be smart to pick Trump, especially if there wasn’t a team of referees to monitor his every move. Some of his tactics are blatant: not counting foul shots, dropping balls closer to the hole, and improving his lies. At Winged Foot, a storied New York course where Trump is a member, Reilly tells us, “the caddies got so used to seeing him kick his ball back onto the fairway they came up with a nickname for him: ‘Pele.’ ” (For those who don’t know soccer, the Brazilian Pelé was one of the best kickers of a ball in history.)

And Trump doesn’t only give himself unfair advantages: he’s also been known to hobble his opponents. On another occasion recounted by Reilly, Trump was playing with Mike Tirico, the sportscaster, who hit a long, soaring second shot into a par five, high-fived his caddy, and headed for the green. When he got there, there was no sign of his ball; it had somehow ended up in a sand trap some fifty feet left of the pin. “Lousy break,” Trump said. Tirico was so befuddled that he took a seven. Afterward, Trump’s caddy told Tirico that his approach shot had actually finished up about ten feet from the hole. “Trump threw it into the bunker,” the caddy said. “I watched him do it.”

Of course, Trump isn’t the first golfer to give himself a mulligan, which is golfspeak for a do-over. He also isn’t the first President to do this. Bill Clinton, an enthusiastic hacker, took so many mulligans that they became known as “Billigans,” Reilly says. But Reilly also points out that “Clinton’s methods were less diabolical and more goofy” than Trump’s are. With this President, the finagling on the course is more serious, “a path to something more important: I win again.”

In tracing the roots of Trump’s cheating, Reilly points out that Trump learned some of his tricks from the hustlers at Cobb’s Creek, a gritty public course in West Philadelphia, which he played when he was studying at the University of Pennsylvania. In searching for deeper motivations, Reilly consults with Lance Dodes, a Harvard psychiatrist, who says, of Trump, “He can’t stand not winning, not being the best. It had to have started very early in his development. . . . He exaggerates his golf scores and his handicap for the same reason he exaggerates everything. He has to. He exhibits all the traits of a narcissistic personality disorder. . . . He’s a very ill man.”

Reilly doesn’t say if he agrees with this diagnosis. But at the end of his book, he raises the question of whether Trump’s cheating matters and answers it in the affirmative. “If you’ll cheat to win at golf, is it that much further to cheat to win an election? To turn a Congressional vote? To stop an investigation? If you’ll lie about every aspect of the game, is that much further to lie about your taxes, your relationship with Russians, your groping of women? . . . I’m glad my dad didn’t live to see a Commander in Cheat like Trump. It would’ve turned his stomach.”

For a sportswriter, that’s quite a bit of editorializing, and yet one senses that Wodehouse would have approved. In “Ordeal by Golf” his alter ego remarks, “I employed a lawyer for years until one day I saw him kick a ball out of his heel-mark. I removed my business from his charge next morning.” The rest of us don’t have that option. For now, at least, we are stuck with Pelé in the White House.