EUROPE was at war in 1941 when Pamela Churchill, Winston Churchill's beautiful young daughter-in-law, first met W. Averell Harriman, the special envoy sent by Franklin D. Roosevelt, Britain was desperate. German U-boats were sinking her ships, the Luftwaffe was bombing the ports, the City of London had burned. To Pamela Churchill, Harriman had come to save England.

She was 21, an English aristocrat who had married Churchill's son, Randolph, soon after their third date. Harriman was 49, an American patrician with a Union Pacific Railroad fortune worth $100 million. They were introduced at Chequers. "He was the most beautiful man I ever met," she remembers. "He was marvelous, absolutely marvelous looking, with his raven black hair. He was really stunning. Very athletic, very tan, very healthy."

Her husband was away at war. Harriman's wife, Marie, was back in the States. Many old friends say the two fell in love then, caught up in the tumult of the time. She will only sigh and say, "I thought him a very, very attractive person . . ." and then drift off.

Now it's 1983, and Pamela Churchill, two husbands and four decades later, has become Pamela Harriman, the third wife of Averell Harriman and, in the last two years, Washington's most improbable political operator. You can find her flying above Mississippi on the governor's jet, speaking to packed ballrooms, keeping political candidates waiting for lunch. Before she leaves on a trip, her maid scurries upstairs with a last-minute glass of orange juice. An assistant carries her papers as the butler opens the front door. "Goodbye!" she calls gaily. Her chauffeur drives to the airport, the jet pilot shakes her hand, a young staffer holds her umbrella, a wide-eyed woman asks for an autograph--and a governor calls her the Democratic Party's new savior.

Pamela Harriman loves it.

From her base on N Street in Georgetown, she has gone after power in the direct way that men often do: carefully setting her goals, then single-mindedly--and unashamedly--pursing them. She is a shrewd professional who has broken the discreet rules of the political hostess set she once belonged to in Georgetown. She is both admired and attacked; people have always said she attached herself to rich, powerful men. She was married to Leland Hayward, the famous Hollywood agent and Broadway producer, in between Churchill and Harriman, and certainly, none of her three husbands or former "beaux"--Italian automobile magnate Gianni Agnelli, French banker Elie de Rothschild and international playboy Ali Khan, to name a few--has been a pauper.

But she is never ignored. Just last week, her husband met with Yuri Andropov in Moscow. There were five men in the room, and Pamela Harriman was right in there with them. "A very impressive-looking man," she said afterward, "but I wouldn't want to play poker with him."

"Pamela likes power," says Robert Strauss, the former Democratic party chairman and one of her close advisers. "A lot of us do."

After Jimmy Carter lost the presidency, she saw an opportunity in the shards, and so started "Democrats for the '80s," her own political action committee. She would raise money for Democratic candidates. Everybody laughed. How was this Georgetown society lady going to revitalize the party of the poor and working class? They called it "Pammy's PAC."

But in 2 1/2 years, she has raised $1.6 million. She gives money across the board, which is unusual--and welcome--in the Democratic Party. In the 1982 election, out of about 300 PACs that aren't attached to interest groups, she ranked as the fifth-largest giver, contributing $359,883--more than Terry Dolan's National Conservative Political Action Committee, which raised almost $10 million but gave out $263,171.

Professionals don't rate her as a serious political broker because party regulars don't go to her for advice or to hear her judgment on candidacies. But a clever politician will ask her what she thinks, and would be unwise not to cater to her. Any Democrat in the country will return her phone calls: Sen. Edward Kennedy , AFL--CIO President Lane Kirkland, New York Stock Exchange Chairman William Batten, black leader Vernon Jordan or presidential candidates Walter Mondale and Ohio Sen. John Glenn.

At a recent fundraiser she organized at a Mobile, Ala., mansion, Atlanta Mayor Andrew Young, former budget director Bert Lance, former Housing and Urban Development secretary Moon Landrieu and Alabama Sen. Howell Heflin dropped by. While the wives watched from the crowd, Pamela Harriman was up at the microphone with the boys. "Our first priority is to win back the United States Senate!" she said. "I, like you, want to see the Finance Committee led by Senator Russell Long! I, like you, want to see the Appropriations Committee guided by Senator John Stennis!" She was glowing, the star of a movie-set party held at a multimillionaire's house where Thomas Sully portraits hung on the walls and the night air blew the Spanish moss in the trees. Men kissed her cheek. During the buffet dinner, she took her plate and sat on the grand staircase, right between Landrieu and Heflin, a political animal at home with the others.

"I consider it the most unique political emergence that I have seen in the many years I've been here," says Clark Clifford, the lawyer who is also her friend and adviser--and who made headlines a year and a half ago when his reference to Ronald Reagan as "an amiable dunce" at one of her parties got out on the street. "She has used the position that Averell gave her with intelligence and wit, and has made a personage out of herself in the process." But don't those more cynical say she's just using her husband?

Clifford smiles. "My answer to that is: 'I never saw anybody used who enjoyed it so much.' "

"I know it's difficult for people to understand," Pamela Harriman says in an English accent that is deep, occasionally croaky and always mesmerizing. "But whatever I've done in life, I've done a little bit with blinkers on. I get set on something, and I do it. Everybody says, 'What's in it for you?' But why should there be anything in it for me? To me, if we can get a Democratic Senate, and a Democratic president, I'm going to retire for the rest of my life . . . I understand if you're a young man or woman, starting out in a profession which you mean to get to the top of, it is important to have power, to have leverage, to move around. But I kind of . . ." She pauses. "That's not what I need."

". . . My son says I'm a bit of a chameleon, and I think he's probably right. Because I don't like things that I don't know. I like to know how things work that I'm interested in. I've often said that I consider myself a back-room person. I think that's what I like."

At 63, Pamela Harriman is still a beautiful woman. She has lines in her face, but her skin still has that expensively cared-for look: silky, lightly powdered, flawless. Her once-red hair is now light brown, but it is thick and smooth, brushed high off her forehead, with a small streak of gray near her temple. She is full-figured, and often choses exquisitely tailored Halston suits with long jackets to flatter her lines. She wears them over and over, unusual for a rich woman, as if to keep people from calling her a clotheshorse. They are in bright colors--purple, deep blue, red--and so the effect is that of a big, powerful woman, with style.

She is sipping iced tea with fresh mint behind the massive oak desk in her office, a large room of elegant beiges and ivories in the brick town house that is next door to her home on N Street. On the wall are pictures of Averell Harriman at the Yalta, Tehran and Casablanca conferences. On a small table is a mounted pen that he used to initial the 1963 nuclear test ban treaty in Moscow. On another table is a picture of one of her horses, Rear Swing, decorated with two first-place ribbons.

She is cautious in an initial interview, but loosens up during a second. She can be charming and almost cozy, telling stories about the French Riviera and Winston Churchill, yet she is always on guard. In public, she has a regal bearing. When she began a recent speech in Jackson, Miss., the women first whispered among themselves, "Now who was she married to?" before they settled in, transfixed by her booming voice and Churchillian cadence.

This year she has launched a "Win the Senate '84" campaign, and already has enough money committed to give the maximum allowed--$5,000 for the primary election and $5,000 for the general--in each of the 33 Senate races. Her new goal is to raise $500,000 to do additional polling and possibly advertising. She hasn't backed a Democratic presidential candidate, so all of them are eager to please. Not long ago at lunchtime at the Four Seasons Hotel, you could see Mondale, the early front-runner, at the concierge desk. Pamela Harriman didn't turn up until 10 minutes later. Mondale waited.

Her last two years have been remarkable; she has seemed to know exactly what to do, and when. It seems as if she spent her first 10 Washington years studying the city and then, sparked by circumstance, got off the ladies circuit and pounced. "I don't think I plan as much as you think I plan," she counters.

But consider that she has:

Courted Charles Manatt, the Democratic Party chairman. It is a mutually beneficial friendship. She introduced Manatt, a party outsider, to Washington's Democratic establishment, and he in turn attends her fundraisers and so lends her PAC credibility. "I couldn't have begun to know a small portion of the people she knows," Manatt says.

Pulled together a board of directors that represents some of the most influential names in the Democratic Party. Among them: Stuart Eizenstat, Carter's former domestic policy adviser, and Edmund S. Muskie, the former secretary of state and senator from Maine.

Cultivated a smart circle. Strauss helps on political matters, such as writing his old friends on her behalf and asking for money. Clifford helps with historical perspective. She reads her speeches to her husband. Sandy Berger, a lawyer and former State Department aide, helps with nuts and bolts. Peter Fenn, a one-time aide to former Idaho senator Frank Church and a respected political person around town, got the PAC off the ground, and has since been replaced by Sven Holmes, who was an assistant to Sen. David L. Boren when he was governor of Oklahoma.

Helped to underwrite projects traditionally paid for by the party, including a 1982 "Fact Book" for Democratic candidates, upcoming polling by the Senate Campaign Committee and a research project that will analyze the Republican record.

Begun to travel across the country, tapping local money sources. Last month at the Mobile fundraiser, she netted $30,000. "Glenn's person told me I was taking money away from them in Alabama, and what did I think I was doing?" she says, relishing the thought.

At the same time, she has used the Harriman house and the mystique of the name to attract people to her events. Giving $1,000 to the Senate campaign of North Carolina Gov. James Hunt is a little less painful when you have dinner within view of the paintings by Degas, Picasso and Matisse that hang in her home. Attending another mammoth Democratic fundraiser at the Washington Hilton is a lot less dreary when it becomes a 90th birthday party for Averell Harriman--a billing that offended some of his old friends when she organized it 2 1/2 years ago. Her PAC split the $440,000 net with the Democratic National Committee.

People still make fun of her "issue evenings"--where some of the nation's biggest egos have dinner, expensive wines and an unremittently serious discourse on the future of the party--but they stop laughing long enough to drop everything and fly in for them. She's had 24 to date, and they've become chic testing grounds for political candidates. Last June, word got out that Mondale "laid an egg" at the Harrimans, and last September, Glenn angrily told guests he didn't have to be Jewish to understand the Middle East. New York Times columnist William Safire eventually used that to explain why he thinks Glenn isn't a supporter of Israel.

At the Harrimans' parties, senators, financiers, writers and diplomats flow through softly lit rooms where the gaze of Winston Churchill stares up from family snapshots. Beyond the glassed-in porch is a terraced garden and pool, lit in the night. Cigarettes sit in tiny holders on the tables, and in the dining room, against a backdrop of wallpaper lush with flowers and birds, are Virginia hams, legs of beef and chocolate rolls. Although Averell Harriman is always at his wife's side, this is her show.

It's hard to understand what motivates her. Why does she work 10-hour days when she could be riding in the country and going to lunch? Is it because she wants a political appointment in the next Democratic administration--or is she really committed to the party?

But one sense you get from her is that she's preparing for the day when her husband is gone. She wants to be a part of the future, and she's trying to create her own niche. "She'll take care of herself," says Averell Harriman. "I'm not made to worry. There are things you have to face in life. You can't tell when someone's going to die. Fortunately, we can provide her something to eat and a place to lay her head."

As she herself says: "It's very nice to have comfort, support, love, all of that. But I think all of us know that there are certain things that you have to be responsible for yourself, and nobody else can. You can't hide behind other people . . . At the end of the day, everybody is alone." Pamela Digby Churchill Hayward Harriman, the daughter of the 11th Lord Digby, has lived the kind of life of which romantic epics are made. She grew up in Minterne, one of England's great country houses, but describes herself as a "round and fat" girl from Dorset who longed for the city. She married Randolph Churchill at 19, then moved to 10 Downing Street. She met Gen. Dwight D. Eisenhower, Gen. George C. Marshall and Irving Berlin.

She was divorced after the war, then went to Paris. She knew Andre Malraux, the writer; Roland Petit, the choreographer, and Rene' Clair, the film director. For almost 20 years she was partner of the salons of the rich, where she was admired and cared for by men like Agnelli, Rothschild, Ali Khan and Edward R. Murrow, the legendary broadcaster. In 1960 she married Leland Hayward. His fourth wife, Slim Hawks (who was also Pamela Harriman's good friend) had introduced them several months earlier, according to Leland's daughter Brooke. After Leland Hayward died in March 1971, Pamela Harriman met Averell Harriman again at an August party in Washington. In the 30 years since the war, he had been U.S. ambassador to the Soviet Union, U.S. ambassador to Great Britain, the governor of New York, America's top negotiator at the 1968 Paris Peace Talks, and a friend and adviser to presidents Truman, Kennedy and Johnson.

He was 79. She was 51. They were married two months later.

In the dozen years since, she has made enemies of the Georgetown political hostesses. They continue to kiss the air behind her cheek, but talk about her behind her back. Many of them have been here since the New Deal, but Pamela Harriman, the newcomer, has eclipsed them in drawing power. They complain among themselves that she is self-centered, and they say she looks down on them, and they resent it. "Could you believe that stuff? one of the ladies said to a friend after a flattering newspaper article appeared about Pamela Harriman. And it's among this crowd, which was aghast when she quickly married the multimillionaire they had known for years, that you can still hear her described with the word "courtesan."

"That's ridiculous," she says. "It doesn't really make any sense atoll. And if I had ever gotten bothered about what people thought, I would never have gone anywhere. I would have gone back to Dorset, married a farmer and raised pigs.

"But if I say, 'I don't care, and then suddenly in the papers it says, 'Oh, I don't give a damn what people say about me,' they'll all say, 'Ahhhhhhh! That's another reason why we think she's a bitch!' " She starts to laugh. "But I don't really care, no!" She laughs again.

Later, she is more reflective. "I think they may say that I don't worry about them, or care about them or things like that, but I mean, I'm not out to do anybody in." Her voice becomes almost a mumble. "I just am not a part of their life. I think they think I'm an oddity."

She has much less to say about Brooke Hayward, her stepdaughter. In her autobiographical book "Haywire," Hayward described her stepmother as a cold-blooded gold digger who once offered to safe-keep some jewels that belonged to Brooke Hayward's mother, actress Margaret Sullavan, --and then never returned them.

"What jewels?" Pamela Harriman responds. "I was never asked to hold any jewels. I never knew her mother had any jewels." And the book itself? "The wicked-stepmother syndrome," she says briskly. "I think it's perfectly normal for a stepdaughter not to like her stepmother. I really do think it's been blown out of all proportion."

"Blown out of all proportion?" says Hayward. "I thought I was extraordinarily restrained." When CBS made a television movie based on the book in 1980, the Harrimans' lawyers saw to it that all references to her were deleted. In her yellow drawing room, you can see a needlepoint pillow that simply says: "Be reasonable. Do things MY way."

Around men and in social settings, Pamela Harriman becomes, by all accounts, a soft, enchanting woman who knows how to cast a spell. "She is a truly eloquent listener," says columnist Joseph Kraft, an old friend of Averell Harriman's. "She can make you feel important and brilliant."

"She understands powerful men who have little cats scratching at their insides," says another old friend. Those close to her marvel at what she has done for her husband, which is to keep him active, even with his hearing and sight problems, at the age of 91. For every person who says that she married him for his money, there is another who counters that she has added years to his life.

Through the years, she has always taken on the identity and interests of her husbands. With Randolph Churchill it was the war, with Leland Hayward it was New York and the theater, and now, with Harriman, it is Democratic politics. But this is the first time she has branched out so extensively on her own--to the point where the traditional roles have been reversed. Now she is the one out front.

During the day, she has old friends come by for lunch with her husband, and when she is traveling on weekends, she makes sure there are guests at their country house in Middleburg. When she made a speech in Raleigh, N.C., recently, she chartered a $2,000 jet because she says she didn't want to be away overnight. "I don't think it's fair to leave him," she says. Although he sometimes complains that she's always on the phone, friends say he worships her.

"She's certainly contributed to making my life full and active," Averell Harriman says in his typically unemotional manner. "I'm certainly grateful to her. She stimulates my activities." Even Brooke Hayward says that Pamela Harriman was "a terrific wife" for her father. "She understood his basic needs," she adds. Pamela Harriman herself says that when she married Leland Hayward at 40, "I think I finally realized that I had what I really wanted, which was a very happy marriage."

During working hours she is as driven as any young career woman in town. "I've always been a bit of a perfectionist," she says. She keeps five separate calendars, requiring her staff to keep them continually updated--even with her husband's dental appointments. After one of her sometime-speechwriters (Berger, Holmes and Alfred Friendly Jr., a former Carter White House aide) has helped with a text, she reworks it, then calls any number of her advisers, sometimes reading just one sentence and asking--even on weekends--what they think. When she takes on a project, she becomes involved in every detail, down to the paper texture of the invitations and the color of the ink.

"There's this built-in crowd in town," says Strauss. "Whenever there's some Democratic event, she gets "Democrats for the '80s" involved, and has a reception or dinner beforehand, or a lunch afterward. She just siphons them in and knocks them off for $10,000. She's smart."

Her houses--Georgetown, Willow Oaks in Middleburg and Birchgrove in Westchester County, New York--are exquisitely done in antiques, porcelains, chintz and art. There are always fresh flowers in every room, from huge vases of tulips to potted amaryllis to silver bowls of extravagant arrangements for the dinner table. She brings many of them back herself from the greenhouse in Middleburg.

"We had one of the great gardens of England," she says. "I've lived so many places, and in so many countries, under so many different circumstances, that I early on got into the thing of trying to make even a hotel room the way I wanted it. Even when we were on the road with plays with Leland, one of the first things I'd do would be to get flowers and do them myself."

In her purses, which come in several colors of alligator, she keeps mints in a delicate silver box. Even the paper napkins she takes along with her for snacks on trips are monogrammed with PCH.

Of her three former names to choose from, she has kept Churchill. arriman grew up in the south of England, a farming land of hills and wildflowers. The town of Dorchester, near Minterne, was the model for Thomas Hardy's Casterbridge, and around it are the heaths he made famous. It was protected and isolated, and she wanted more.

She learned French at home, then went to boarding school in Germany. At 18, she was presented at court to London society. "I found it very frustrating," she says. "All these silly dances where we had to have our parents come and sit around and watch it all. I felt very much out of it because I didn't know a lot of people. I was terribly, terribly overworried about the fact that all I knew how to do was to ride a horse. I longed to be sophisticated. And my mother was very strict. They wouldn't allow us to wear makeup.

"I was brought to America when I was 17, and I was allowed to bring two evening dresses. I wasn't allowed to pay more than eight pounds for them, and they were rather tacky, I suspect. Also, I was not allowed to wear black, or dark clothes, and it was the middle of winter. So I was given a sort of chiffon evening dress, in a light color. And the first night I went out in New York, somebody said to me, 'Oh, in England do they really wear chiffon in winter?' And I knew it was all wrong! I knew! God, it was awful."

Back home, she found a job in the Foreign Office, then met Winston Churchill's son, Randolph, 27. The Wall Street Journal called him bibulous. He proposed after two or three dates. "At the time, he absolutely swept me off my feet," she says. "It was a time when most of the men I knew, young men, were scared. They were going off to war, they were going to get killed. And here was Randolph, who was absolutely certain that the war was going to be long and bloody and terrible, but of course we were going to win. And that was very appealing. Here was somebody who had total confidence."

They were married Oct. 4, 1939. At the time, Winston Churchill was first lord of the admiralty. Randolph returned to war a few days later. The following May, after Churchill had become prime minister, Pamela--pregnant with her only child, Winston Churchill--moved with her father-in-lawto Downing Street.

One of the first Americans she met was Harry Hopkins, Roosevelt's initial wartime emissary to Britain. "And Harry was a dear," says Pamela Harriman, "but you know he was all bunched up, and looking desperately sick, and had a few wisps of hair and a dead cigarette hanging out of his mouth day and night. He was a wonderful man, but he wasn't quite a pinup." Next came John Gilbert Winant, the new U.S. ambassador to the Court of St. James's. "The joke was that Winant always looked like Lincoln and tried to," Pamela Harriman says. "You know, he had a lock of hair coming down and he was dramatic-looking."

And then there was Averell Harriman. "Averell was just beautiful," she says again.

"Hopkins told me she had more information than anyone in England," Averell Harriman recalls.

It was an incredible time for a young woman. "I've often thought since, 'Did I realize?'" she says. "If I had, I would have kept diaries." Later, she says: "Harry Luce once told me, in the war, that 'Clare and I always write for 40 minutes every night before we go to sleep.' And I remember thinking, 'Oh, what a goddamn bore!' Imagine! If something exciting has happened during the day, the last thing you want to do is write it down."

During the war, she also ran the Churchill Club, an idea of Brendan Bracken, Churchill's parliamentary private secretary. It was a place where American officers in London could get a drink or a meal and listen to a speaker--sometimes T.S. Eliot, or sometimes Sir Kenneth Clark. "And he used to be a fill-in," she says, "when we had a top guy who didn't appear at the last minute." Sometimes Irwin Shaw, James Stewart or Clark Gable would come by.

At the same time, she had become a favorite of her father-in-law. "There was a lot of humility in Winston," she says. "Everybody thinks that he was so geared up and full of himself. It wasn't that at all. He knew that he had the power to save England, and to build the morale of the people . . . but he would often put his head in his hands, at lunch or at supper, and be very, very down."

At the war's end, after Averell Harriman had gone back to America, she and Randolph were divorced. She thought about a political career, but instead went to work for Lord Beaverbrook's Evening Standard. "And then," she says, "I suddenly woke up one day, and said, 'My God, you've never had any fun.' " She headed for Paris.

Paris in the '50s was recovering from the war, but was still the center of thought and style. "I shall always love Paris," she says. "Oh, I had lots of beaux." But wasn't she--underneath--a little unhappy, drifting from man to man, not knowing what she was doing?

She laughs. "I knew exactly what I was doing."

It was on one of her yearly trips to America that she met Leland Hayward. He was married at the time. It was a fast courtship. As Brooke Hayward recounted in "Haywire," Leland Hayward had escorted Pamela Churchill to the theater one night in New York at the insistence of his wife, Slim Hawks, who was away for two weeks. They were married soon after he got a divorce, and stayed married for 11 years, until his death from a stroke. Pamela Harriman says it was the hardest time of her life. "He was too young to die," she says. "And it was, I guess, an overwhelming shock to me. And then I kind of was stymied, you know. I'd always been able to live happily on my own, and I was sure that I would and could, but to pick up again . . ."

That summer she went to England and the south of France. She came back to New York in August. "You know those sort of awful August days when there's no sun, everything is sort of dark and raining and it's not summer?" she says. "And I came home to an empty house--and the depression of coming back." There was a message to call Katharine Graham, now the chairman of the board of The Washington Post Co., because she wanted to ask her to a party. Pamela Hayward accepted.

And there stood Averell Harriman, in the garden. His wife, Marie, had died the year before. He hadn't seen Pamela for almost 20 years. "It was very strange, she says. "Because the moment we started talking, there were so many things to reminisce about that one really hadn't thought about for years. Anyhow, it all--" she sighs--"it all had a fairy-tale ending." arriman's chartered jet takes off from Raleigh, N.C., headed home toward Washington. She has finished her speech to the Democratic Women of Wake County. It was a party pep talk, and they gave her a standing ovation.

She breaks out a lunch prepared by her chef: French wine, chef's salad, carrot sticks, cheeses. "Well," she says, as the plane heads above the clouds, "we didn't let them down!" She talks excitedly about upcoming events, and the two staffers with her eagerly take notes. She was up before 5 a.m., worrying about her speech, but now she's feeling relaxed and pleased with herself.

Back when she was a 25-year-old reporter for the London Evening Standard, she once wrote a story from Monte Carlo about Peggy Joyce, a "beautiful blond American." Pamela Harriman had never met Joyce, but she visited her old house and talked to her friends. When she was finished with her reporting, she had enough insight to write:

"Everyone knew her. She had that careless, confident walk which women acquire when they know that all eyes turn toward them when they enter a room. Peggy Joyce had made a life for herself. She had had lucky breaks, but she had known what she wanted."

She could have been describing herself.