The invitation of President Trump to next month’s Ryder Cup matches at Bethpage Black marks a dramatic shift from four years ago, when the PGA of America said hosting a tournament at one of his courses was “detrimental” to its brand. The red carpet is now out where the door was once firmly closed.

It seems like ancient history now, but following the January 6, 2021, Capitol riots, the PGA swiftly distanced itself from Mr. Trump. Less than a week after pro-Trump supporters caused chaos at Washington, the organization’s board of directors voted to pull the 2022 PGA Championship from Trump National Golf Club at Bedminster, New Jersey, saying holding a major championship at one of his properties would put the organization’s ability to function “at risk.” What was once a prized venue in their eyes had become a liability.

Mr. Trump has a long memory when it comes to those he believes have wronged him, but all seems to be forgiven when it comes to golf and his once adversarial relationship with the PGA of America and PGA Tour.

The Ryder Cup, pitting America’s top professional golfers against a squad of European players, is the PGA’s marquee biennial event. Mr. Trump recently announced on Truth Social that he’ll attend the matches at Bethpage on September 26, the first day of the three-day competition.

“At the invite of the PGA Tour, I will be there on Tournament Friday!!! President DJT,” Mr. Trump posted, making the common mistake of confusing the PGA Tour with the PGA of America.

Mr. Trump had issues with both organizations during his first term as president. In 2016, the PGA Tour ended an agreement to hold its annual World Golf Championship at Miami’s Trump National Doral after he made what were viewed as disparaging remarks about Mexican immigrants. The event was moved to Mexico City.

The United States Golf Association held its 2017 Women’s Open at Trump National at Bedminster, but moving the 2022 PGA Championship out of New Jersey was embarrassing to the outgoing president and seemed to end one of his most valued partnerships.

Mr. Trump is more than an avid golfer. The Trump Organization, operated by his sons Don Jr. and Eric, owns 17 private and public courses throughout the world, including one at Dubai, and relishes the prestige of hosting major tournaments.

Whether it was to get back at the PGA Tour and the PGA of America or simply a shrewd business move, Mr. Trump aligned with LIV Golf, a rival league that began play in 2022 funded by Saudi Arabia’s Public Investment Fund.

LIV Golf staged events at Doral for four consecutive years, helping legitimize an organization that was poaching many of the PGA Tour’s top players. Mr. Trump also hosted a LIV Golf event at Bedminster during the league’s inaugural season. Trump National Golf Club outside Washington, D.C., also featured LIV Golf, further strengthening its ties to venues owned by the Trump Organization.

Despite widespread unease over Saudi Arabia’s human rights record, Mr. Trump trumpeted his association with LIV Golf.  “All of those golfers that remain ‘loyal’ to the very disloyal PGA, in all of its different forms, will pay a big price when the inevitable MERGER with LIV comes,” Mr. Trump posted in 2022, adding, “I made a deal with them. They’re very good people. They’re very fine people.”

All seems forgiven since his re-election. Mr. Trump has been actively working to promote a merger between LIV Golf and the PGA Tour. He summoned officials from both leagues to the White House in February for talks that were characterized as “a constructive working session.”

Tiger Woods, the PGA Tour commissioner, Jay Monahan, and the LIV Golf chairman, Yasir Al-Rumayyan, were among those in attendance. All credited Mr. Trump for his efforts though no settlement appears in sight.

“We know golf fans are eagerly anticipating a resolution to negotiations with the Public Investment Fund and want to thank President Trump for his interest and long-time support of the game of golf,” the PGA Tour said in March.

“We asked the President to get involved for the good of the game, the good of the country, and for all the countries involved. We are grateful that his leadership has brought us closer to a final deal, paving the way for reunification of men’s professional golf.”

Attempting to broker a merger has helped Mr. Trump go from persona non grata to coveted by not only LIV Golf, but the PGA of America and the PGA Tour. In addition to being invited to the Ryder Cup, his courses have returned to the PGA Tour schedule.

The PGA Tour returns to the Trump Doral’s Blue Monster next May for a Signature Event that is being called “The Miami Championship.” His Turnberry Course in Scotland is also being considered for a future British Open.