At Menendez’s Island Resort Fund-Raiser, Donors Were Scarce. So Was He.

At Puerto Rico’s most exclusive beachfront resort, where shoulder season rooms go for $1,500 a night, deep-pocketed donors have reliably lined up to pay tribute to Senator Robert Menendez in the form of a $5,000 check to his political action committee.

But this year’s retreat imploded, as donors quickly distanced themselves from Mr. Menendez after he was indicted on federal bribery charges, turning the once powerful Democrat from New Jersey into a pariah at his own fund-raiser last weekend.

The opening reception on Friday evening was pared down to three small tables overlooking the beach. There were still open seats: Only about a dozen people showed up to the subdued affair and roughly half of them were the senator’s aides. Trays of sushi and shrimp cocktail were left uneaten.

The shunned senator never showed, absent at his own ill-timed and ill-fated fund-raiser.

More than half of the 50-or-so donors and their guests canceled attendance after the senator was charged three weeks ago. A defiant Mr. Menendez refused to cancel the retreat despite the defections. Then, as he landed in San Juan on Thursday, he was buffeted with more untimely news: Prosecutors filed additional charges and asked a judge to seize his home.

The fund-raiser would normally have given donors a prime opportunity to get access to the senator and his team, lobbying for various causes in a relaxed setting. The retreat was supposed to include a round of golf with Mr. Menendez and a poolside lunch with his chief of staff.

But the awkward prospect of mingling with a scandal-ridden senator caused many of the remaining donors to pull out just a day before the retreat. In the end, only a handful of guests and their partners made the trip to Puerto Rico, but even some who stayed at the resort did not turn up to the scheduled receptions.

Neither did Mr. Menendez.

The annual retreat’s collapse was a stark reflection of the senator’s sudden isolation and diminished stature, abandoned by droves of one-time allies as he fights for political survival. It also underscored the uphill climb he could face to raise money to pay for an expected re-election campaign and for lawyers to fight corruption accusations he has vehemently denied.

About 1,500 miles away in New Jersey, an air of inevitability of Mr. Menendez’s imminent political demise has settled in, after the senator was accused of using his elected office to benefit the Egyptian government and three business men in return for bribes that included wads of cash, a Mercedes-Benz convertible and gold bullion bars.

Donors said they turned down requests from Mr. Menendez’s finance director to contribute to his defense fund. A 41-year-old New Jersey congressman, Andy Kim, announced he would challenge the senator in a Democratic primary. And other potential candidates began to work back channels as they assessed whether to make a run for Mr. Menendez’s seat, including the wife of Gov. Philip D. Murphy, Tammy Murphy, who has never even held elective office.

The political pall surrounding the senator extended to Puerto Rico, where he and his wife kept a low profile at the hotel, the Ritz-Carlton Reserve at Dorado Beach, a high-end resort about a 30-minute drive west of San Juan that is lined with 2.5 miles of beach and dotted with golf courses and massive villas.

The senator skipped both the welcome and farewell receptions. It is unclear if he played golf with donors as he was scheduled to do so on Saturday morning; an employee at the golf course said Mr. Menendez did not appear to have a tee time. But he did emerge from hiding to have a solitary dinner with his wife, Nadine Menendez, who has also been charged in the bribery scandal.

In many ways, the 1,900-acre natural reserve is an ideal hideaway for a politician looking to escape controversy or to mingle, away from prying eyes: It is only open to residents, local members and guests willing to pay as much as $4,500-a-night for an oceanside suite during hurricane season.

For the past few years, it has served as the go-to venue for Mr. Menendez to host scores of lobbyists from blue-chip corporations and to raise money for New Millennium PAC, which Mr. Menendez, known as a prolific fund-raiser, has long used to steer generous contributions to other lawmakers and candidates to increase his clout among colleagues in Capitol Hill.

Samantha Maltzman, a spokeswoman for the New Millennium PAC, denied that the retreat had been a failure and did not say how much was raised.

“The fund-raiser was very successful, and, in fact, the senator and his wife did have drinks/meet with several of the attendees,” she said in an emailed statement. “We look forward to hosting the event again next year, however, we will not comment further as we always preserve the privacy of our guests.”

New Millennium PAC has raised more than $5.2 million since Mr. Menendez was elected to the Senate in 2006, amassing contributions from big corporations like Microsoft, Pfizer, Wells Fargo, General Motors, AT&T and Fox Corp. While it has showered lots of that money on other candidates and campaigns, Democrats in competitive races returned or donated some of those contributions when Mr. Menendez was accused in a different corruption case eight years ago.

There are few restrictions on how Mr. Menendez can spend the money.

In 2014 and 2015, for example, the PAC transferred $20,000 to the legal defense trust that Mr. Menendez assembled to help pay for the lawyers that represented him when he was accused in the earlier corruption case. (Mr. Menendez was acquitted in that case after the trial ended in a hung jury in 2017.)

The PAC had just over $600,000 in the bank at the end of June, while his campaign account, which he could also tap to finance his legal fees, has roughly $8.6 million, according to the most recent filings.

Among the few supporters who did attend the retreat this year was Michael Hutton, a lobbyist who served as Mr. Menendez’s chief of staff in the House of Representatives in the 1990s and early 2000s. Mr. Hutton, who runs his own lobbying firm on K Street, has appeared to keep close ties to Mr. Menendez since he switched to the private sector.

After Mr. Menendez was first sworn in to the Senate in 2007, Mr. Hutton reportedly threw him a private party in Washington, D.C., that was funded by corporate donors. And he has made at least $70,000 in contributions to Mr. Menendez’s campaigns and PAC over two decades.

Mr. Hutton did not reply to a request for comment on Monday.

Also present at the receptions was Javier Ortiz, a partner at an investment firm, Falcon Cyber Investments, who has donated mostly to Republican politicians, including former President Donald J. Trump, according to filings. He has also given $37,000 since 2017 to Mr. Menendez’s campaign and PAC.

Reached for comment after the retreat, Mr. Ortiz would not to say if he had met with Mr. Menendez and pointed to the senator’s presumption of innocence under the U.S. legal system.

“I’m an American that supports Americans,” he said repeatedly during a brief phone interview when asked about his attendance.

After so many donors dropped out this year, the retreat was relegated to more of a weekend getaway for Mr. Menendez and his staffers.

On Saturday evening, the senator’s chief of staff, his press aides and a hired fund-raiser gathered with a handful of guests for the retreat’s farewell reception and mingled by the beach over plantain chips and seafood appetizers.

Down the beach, Mr. Menendez donned dark pants and a blue tucked-in polo shirt as he strode into the hotel’s pricey restaurant with Ms. Menendez. They appeared to sit alone for a quick dinner, then disappeared again.

Under the terms of their indictment, Mr. Menendez may continue to travel for official business; his wife, who surrendered her passport, is required to obtain permission from a federal judge or prosecutors if she wants to travel outside of New Jersey, New York, Washington, D.C., or Florida.

The couple’s stealth presence in Puerto Rico was noted by hotel guests, with one discussing the sighting with a friend at the hotel bar, where guests sipped on $25 cocktails over live bossa nova music.

“It seems like the best way to get out of the spotlight for bribery is to go to the most expensive resort in America,” the guest quipped.

Tracey Tully contributed reporting.