“Pretty nervy of you to come to this club,” Trump snapped.

His ire was aimed at Jeff Greene, a real estate tycoon from Palm Beach and Mar-a-Lago member who ran for Florida governor in the Democratic primary last year. Greene said he wasn’t surprised by the reception. A year earlier, he and the president had gotten into a shouting match at the golf club that he videotaped and then featured in political ads across the state.

After the chilly exchange, which Greene described to POLITICO, everyone parted ways and went to the club’s dining room for a bite. But the president didn’t let it go. Sitting at a separate table in the dining room overlooking the golf course, Trump twice yelled across the room at Greene according to his retelling.

“You spent millions of dollars and came in fifth!” Trump taunted, according to Greene.

“I came in fourth!’” Greene said he called back.

Former Florida Democratic gubernatorial candidate Jeff Greene. | Wilfredo Lee/AP Photo

In Palm Beach, word spread that there was a new chapter in the spat between Trump and Greene. And while it might seem like a petty squabble between two rich Floridians, the exchange highlights a broader truism about Trump — he doesn’t let things go.

Whether in the privacy of his clubs or out on the campaign trail, the president can’t help but hold onto a grudge. Even as Trump heads into an election year with a record that he claims ranks him among the best presidents of all time, political grievances continue to drive everything from policy decisions to rally speeches to some of the biggest scandals of his presidency — including his impeachment.

The Ukraine quagmire arose from a quest to dig up dirt on a Trump political rival, former Vice President Joe Biden and his family. While explaining his reasoning for striking Iranian military leader Qasem Soleimani, Trump invoked former president Barack Obama, his favorite punching bag until Hillary Clinton entered the picture. During remarks about a China trade agreement, the president randomly mocked former FBI Director James Comey, saying he had “choked like a dog.”

The White House declined to comment.

To those who know Trump, the refusal to drop any grudge is tied to Trump’s desire to quash his enemies — both perceived and real.

“More than Biden, the president is in this pickle because of his belief that Ukraine meddled against him,” said Sam Nunberg, a former Trump campaign aide. “His primordial instinct to exact revenge can sometimes — as in this case — completely backfire.”

Some of the biggest controversies of Trump’s presidency have swirled around the president’s inability to let go of apparent slights: his antagonism toward the late Sen. John McCain, his spat with the Gold Star Khan family, his attacks on San Juan Mayor Carmen Yulín Cruz in the wake of natural disasters. Even his profane remarks about the NFL when players kneeled during the national anthem could be linked to a failed bid to buy the Buffalo Bills.

For some who have known and studied Trump for years, the president’s penchant for turning personal grudges into larger public and political controversies is nothing new.

“When people get in his way, he has no patience for it and it becomes a personal vendetta even when it shouldn’t and when it’s against his own self-interest,” said Tim O’Brien, a Trump biographer.

“He’s ungoverned around that — he won’t take advice, he won’t look to getting more informed — he will simply do whatever he wants,” added O’Brien, currently a senior advisor to Mike Bloomberg’s presidential campaign. “He’s used to getting away with that because he was insulated from his own mistakes his whole life. His family and his money helped protect him, and then he became a celebrity and he enjoyed the halo of protection that celebrity has, and now he is president he enjoys legal protections.”

O’Brien pointed to an ugly fight between Trump and then-New York Mayor Ed Koch about zoning for a large piece of undeveloped land Trump purchased on Manhattan’s West Side.

Sen. Lindsey Graham carries his golf clubs after golfing with President Donald Trump. | Susan Walsh/AP Photo

“They got in this hilarious, sophomoric cage fight in the tabloids and Trump reveled in it, but it wasn’t what he should have been doing because he lost the deal and almost went bankrupt,” O’Brien said. “So he got into a fight that was in the press, but he didn’t get the project built.”

There have been times when Trump’s grudges-turned controversies have worked in his favor. In the heat of his battle with the NFL, the Trump campaign fundraised off the issue, while some football fans who supported Trump burned their jerseys in protest.

A former Trump aide noted that his supporters appreciate his pugilism.

And the president has converted some of the targets of his political vitriol. Sen. Lindsey Graham (R-S.C.), who Trump once labeled an “idiot,” is now a staunch ally and golfing partner. Sen. Ted Cruz (R.- Texas), who faced nasty Trump barbs about his wife’s appearance and conspiratorial insinuations that his father was involved in John F. Kennedy’s assassination, now stands by him in Congress. And Sen. Rand Paul ( R-Ky), who Trump once called a “brat” with a “badly functioning brain,” has championed some of Trump’s more controversial military actions.

“I can say ‘Gee, he’s a boorish guy, pushes through things, he operates from the seat of his pants at the moment and talks first and thinks later,’” Greene said. “But it works for him.”