One morning in the mid-1990s, Mark Mulvoy was on the sixth hole of Long Island’s Garden City Golf Club with Donald Trump when the skies opened, and they ducked for cover under a nearby awning. The rain let up a few moments later, and Mulvoy, then the managing editor of Sports Illustrated, returned to the green. When he got there, he found a ball 10 feet from the pin that he didn’t remember seeing before the storm.

“Who the hell’s ball is this?” he said.

“That’s me,” the real estate mogul said, according to Mulvoy.

“Donald, give me a f—— break,” Mulvoy recalls telling him. “You’ve been hacking away in the g—— weeds all day. You do not lie there.”

“Ahh, the guys I play with cheat all the time,” he recalls Trump replying. “I have to cheat just to keep up with them.”

It’s a story that the current GOP front-runner hotly denies. “I don’t even know who he is,” Trump said when asked about Mulvoy’s account.”I don’t drop balls, I don’t move balls. I don’t need to.”

But just as Trump has emerged as a national phenomenon by tearing up the rule book of electoral politics, it appears the mega-developer’s willingness to bend the rules may apply to his philosophy of the links as well.

The Donald is known for describing himself as a man of unbridled accomplishment and success in virtually every area he’s attempted, and his golf game has long been one of his most highly self-touted skills.

“I’ve played a lot, and I’ve played well,” he said. “There’s very few people that can beat me in golf.” On multiple occasions during his campaign, he has let voters know that he “killed” U.S. Sen. Rand Paul when the two squared off this year. “I could play him a thousand times and never lose to him,” he said. And by all accounts, Trump is a very good golfer. Just maybe not as good as he says he is.

“The worst celebrity golf cheat?” the rock star Alice Cooper said in a 2012 interview with Q magazine. “I wish I could tell you that. It would be a shocker. I played with Donald Trump one time. That’s all I’m going to say.”

(“I’ve never played with Alice Cooper,” Trump said. “That’s a terrible thing to say about people, especially me.”)

“Golf is like bicycle shorts: It can reveal a lot about a guy,” said Rick Reilly, the sportswriter who hit the links with Trump for his 2004 book “Who’s Your Caddy?” in which he lugged clubs for several of the world’s best golfers and VIP amateurs.

As for Trump? “When it comes to cheating, he’s an 11 on a scale of one to 10,” Reilly said.

Reilly told The Washington Post about an afternoon when Trump wrote down scores he didn’t actually achieve on his scorecard, conceded putts to himself by raking the ball into the hole with his putter rather than striking it properly (“He rakes like my gardener!”), and even called a gimme — something a player might claim for a two-foot putt — on what should have been a chip shot.

“He took the world’s first gimme chip-in,” Reilly said. At one point, Trump, after taking a number of second shots, told Reilly to “make sure you write that I play my first ball. You don’t get a second ball in life.” In life it may or may not be true that a person gets a second chance; and yet, as Reilly wrote, on holes 1, 13 and 17, Trump did indeed get a second ball.

Trump disputes Reilly’s entire story as well: “I always thought he was a terrible writer,” he said. “I absolutely killed him, and he wrote very inaccurately. I would say that he’s a very dishonest writer. … I never took a gimme chip shot. … I don’t do gimme chip shots. If I asked his approval, that’s not cheating, No. 1. No. 2, I never took one.”

But Reilly noted something else about playing with Trump that is echoed by others who have played with him: He had an amazing time. Trump played with confidence and bravado, he tipped the caddies, he gave great pointers that helped his comrades with problem swings. So what if he cheats? The guy is a lot of fun!

“It’s his limo ride, his golf course. The guy paid for lunch — what are you going to do?” Reilly said. “He’s exhausting, but I want to be clear: I really liked him. It was just like being in a crazy carnival for a day. Though I’m not sure it would be so much fun when it starts to count.”

Tony Kornheiser of ESPN played with Trump in 2008 and said in an email Trump “couldn’t have been more gracious or more fun.” Fox News anchor Bret Baier, who recently went toe-to-toe with Trump at the first debate, has played with the real estate mogul and said he was actually very nice when separated from a television camera.

Jonathan Carr spent the 2007 and 2008 golf seasons caddying at Trump National in Bedminster, New Jersey. He remembers a gregarious club owner who treated the caddies with the utmost respect, a man who, despite lacking a “pristine” golf swing, played at a high level of skill and an even higher level of confidence. Carr never saw Trump come close to bending the rules, although he said everyone who caddied there had heard of that reputation.

“The caddies would say, ‘If I get on his bag, I’m going to make sure he always has a good lie,’” Carr said, meaning even if Trump shanked a ball, the caddies would do what they could to place it on the fairway.

And judging by Trump’s own account, he’s had plenty of good lies. He said he holds the amateur record on his golf course in Palm Beach, a 66. In a story about celebrity golf handicaps, Forbes reported his is at a four but noted they have yet to see “a real signed scorecard.”

From a guy who once went on a mission to get President Barack Obama to release his birth certificate, this raises some eyebrows. Ironically, Trump only had nice things to say about the president when it came to his golf game.

“His swing looks like it’s coming along beautifully. His game looks much better,” he told The Post. “I’d love to play him for the presidency.”

Not so much for one of his main opponents, Jeb Bush: “I’d love to play Jeb for the presidency,” he said, adding, “That would be even easier than running against him in politics.”

Trump has shown that his candidacy is immune to the types of attacks that can bring down normal Republican candidates. He’s on record mocking Republican John McCain and praising Democrat Nancy Pelosi, he’s advocated for higher taxes, donated to Democrats and called for single-payer health care. None of that has mattered. But does his golf history provide opponents with the opening they need?

Danny Diaz, Jeb Bush’s campaign manager, tweeted recently, “FACT: Former House speaker Will Weatherford said ‘he did not remember @realDonaldTrump shooting 72.’ ”

But perhaps even this attack could backfire. The only other person Reilly remembers cheating as much as Trump? None other than former President Bill Clinton.

Maybe Trump’s cheating is his most presidential move yet.