About 2 a.m. Oct. 7, 1974, U.S. Park Police pulled over a silver-blue Lincoln Continental that had been swerving and speeding without headlights near the Jefferson Memorial in Washington.

A female passenger in an evening gown ran from the car, climbed the stone parapet along the Tidal Basin and — acting on what she later described as a frantic impulse — leaped headfirst into the frigid, inky water. Her splashdown would ripple into one of the capital’s most infamous sex scandals.

The woman, 38-year-old Annabel Battistella, was a plumage-shaking striptease dancer with the stage name Fanne Foxe. She was billed as “the Argentine Firecracker,” and patrons of the local burlesque circuit were captivated by her elaborate costumes — complete with five-foot-tall headdresses and tropical-colored ostrich and pheasant feathers — as well as the artfulness with which she removed them.

Ms. Battistella at the Tidal Basin in Washington in 1975.

On that particular night, after a boozy party at the Silver Slipper club, where she had performed, she got into a loud quarrel with her married lover. Amid the flow of alcohol and epithets, a friend who was driving them had forgotten to turn on the car’s headlights, attracting the attention of police, who trailed them from the club on 13th Street NW.

A TV crew, alerted by radio traffic on the police scanner, soon arrived.

With her plunge into the Tidal Basin, Ms. Battistella (later Annabel Montgomery), who died Feb. 10 at 84, secured her place in the annals of political scandal. Standing near the car — drunk and bleeding — was her paramour, 65-year-old Wilbur Mills, the gravelly voiced chairman of the tax-writing House Ways and Means Committee and a man esteemed as a pillar of Bible Belt rectitude and respectability.

The Arkansas Democrat, an ascetic grind who shepherded Medicare and other influential legislation through Congress, was also widely regarded as the most powerful man in government after the president. “I never vote against God, motherhood or Wilbur Mills,” a Democratic colleague once told a reporter.

But on that October morning, Ms. Battistella’s eyes were bruised. Mills’s Coke-bottle glasses were smashed, and his nose was badly scratched. He reeked of alcohol. And his 16-year hold on the federal purse strings was suddenly imperiled.

Washington has a long history of tawdry scandals, but the contrast between Mills’s public persona and the subsequent revelations about his private life — his heavy drinking, his frequenting strip clubs, his regular companionship with a star ecdysiast — drew intense media attention as he headed into his first serious reelection fight in more than three decades.

The Mills incident broke almost two months after President Richard M. Nixon resigned because of the Watergate scandal, and “the press was drooling for something like this to happen, looking for another Watergate,” Bill Thomas, author of “Capital Confidential: One Hundred Years of Sex, Scandal, and Secrets in Washington, D.C.,” said in an interview. “The atmosphere had changed, the press had changed, and the hunting season had been prolonged.”

In the weeks after the Tidal Basin episode, Mills maintained that Ms. Battistella — a divorced mother of three at the time and a resident of the luxury apartment tower where he lived in Arlington, Va. — was a family friend and a social companion of his wife, Clarine.

On the hustings, he campaigned with Clarine by his side and a folksy credo: “Never drink champagne with a foreigner.” He won the race that November but continued to see Ms. Battistella and, by her account, deluge her with calls, professions of love and promises of marriage.

Ms. Battistella, meanwhile, spoke publicly of her love for Mills, telling interviewers that she was drawn to “mature” men after a troubled first marriage. “I’ve been around too long,” she told The Washington Post. “I may act sometimes like I’m 18, but I feel like I’m 50.”

As much as she cared for “Mr. Mills” — he was always “Mr. Mills” to her in public — she conceded that they had a volatile relationship. At one point, she claimed, she had become pregnant with his child and had an abortion to save his reputation. Increasingly, she said, his possessiveness conflicted with her need to make a living.

Ms. Battistella — christened “the Tidal Basin Bombshell” — was inundated with striptease offers that paid more than five times the $400 a week she had been drawing at the Silver Slipper. Mills pleaded with her not to bare herself again publicly.

“Mr. Mills wanted me to stay home . . . to study and get a job,” she told The Post at the time. “He wanted me to leave the whole [stripping] thing in the Tidal Basin. But my going back to work started the whole thing up again . . . not because of the publicity but because I promised him for the kids’ sake I wouldn’t go back to being a stripper.”

Fresh off reelection to his 19th term in office and reportedly fortified with two bottles of vodka, Mills appeared in the wings during a performance by Ms. Battistella at Boston’s Pilgrim Theatre. As Mills teetered onstage, she later said, she tried to make light of the situation, announcing: “Ladies and gentlemen, I have a visitor for you, and he wants to say hello. Mr. Mills, where are you?”

“Here I am!” he declared as he wandered out grinning. The crowd, which included reporters who had been tipped to his presence, began to holler, whistle and stomp. Mills took a microphone and walked to center stage, rambling incoherently.

Then, backstage, Mills delivered one of the most excruciating news conferences ever captured on film. Slurring his words, and with barely controlled fury, he declared that all Ms. Battistella’s future performances were off, as she struggled to defuse his wrath.

Back in Washington, Mills was removed as Ways and Means Committee chairman and sought treatment for alcohol addiction. He claimed to have no memory of the entire year of 1974 and blamed his indiscretions on mixing alcohol with “some highly addictive drugs” for back pain. With his career in tatters and citing exhaustion, he left office in 1977 and became an advocate for recovering alcoholics until his death in 1992.

Ms. Battistella prospered — for a while — and wrote of her unyielding loyalty to Mills even after he disappeared from her life.

“I remember being very upset,” she told The Post in 1981, “because he went on interviews and he’d talk about how he didn’t remember what happened to him . . . and, you know, that we were just friends, and he kind of denied the whole thing — without putting me down, of course. The only time he put me down was when he said, ‘I learned not to drink with foreigners.’ . . . I thought, ‘Why doesn’t he keep quiet if he doesn’t have anything nice to say about me?’ ”

Annabel Edith Villagra was born in Nueve de Julio, a cattle-ranching village southwest of Buenos Aires, on Feb. 14, 1936. Her parents were nurses. She described herself as an athletic tomboy who excelled at basketball, shooting wild game and rigorous folk dancing.

She said she had been a pre-med student at the University of Buenos Aires but left at 20 to marry Eduardo Battistella, a cabaret and cocktail pianist. In her memoir, “The Stripper and the Congressman” (1975) — ghostwritten by Yvonne Dunleavy — she described Eduardo as a relentless philanderer who initiated her into partner-swapping. She began dancing in club acts, appearing with him, in part, to keep her eye on him.

By the early 1960s, their itinerary included Miami, where Ms. Battistella began stripping for extra income, and then Baltimore. Along the way, her agent changed her “sweet-sounding” name to Fanne Foxe.

Her marriage had imploded by the time she arrived in the Washington area in the late 1960s, but she allowed Eduardo to live with her at Arlington’s Crystal Towers, she told The Post, “because I don’t like him to spend money, and he is the father of my children.” Money was tight, she said, because she had exhausted her savings on plastic surgeries.

In summer 1973, she met Mills at the Silver Slipper through a mutual friend billed as “Carmen, the Peruvian Love Goddess.” Mills and his wife moved into Crystal Towers, and the Battistellas reportedly played bridge with them until the Tidal Basin plunge. (Ms. Battistella later said that she made the jump out of fear of hurting Mills’s public image and that she might somehow lose her own recently acquired U.S. citizenship.)

After her relationship with Mills became public, Ms. Battistella made the rounds on TV and parlayed her notoriety into starring roles (clothed) in low-budget films and an off-Broadway production called “Women Behind Bars.” She gave up exotic dancing after she was arrested in December 1974 at a club near Orlando and charged with public indecency. A judge cleared her of the charge.

The next year, she was living with her children in Westport, Conn., in an eight-bedroom, seven-bath manse called Tally-Ho that needed constant upkeep. The only stripping she was doing, she told a reporter, involved paint.

She married a contractor and businessman, Daniel Montgomery, in 1980 and had a daughter, Melanie. At some point, she made her way to Florida and settled in the St. Petersburg area.

According to the death certificate issued by the state of Florida, she died at a hospital in Clearwater, but no further details were available. The family’s death notice in the Tampa Bay Times listed survivors as three children from her first marriage — Grace, Alex and Maria — and seven grandchildren. Her daughter Melanie, who according to her death notice became a registered nurse, died in 2017.

Little is known of Ms. Battistella’s later life as Annabel Montgomery, although the University of Tampa said she graduated in 1995 with a bachelor’s degree in communications, and the University of South Florida confirmed she received master’s degrees in marine science in 2001 and in business administration in 2004.

“What happened happened, so that cannot be repaired completely,” Ms. Battistella told The Post in 1981. “But sometimes things can be mended enough to allow you to live comfortably and not be completely ashamed of yourself.”

Andrew Meacham in Largo, Fla., contributed to this report.