When Jeffrey Archer was 3, he wanted to be 4. When he was 4, Archer says, he wanted to be prime minister.

Instead, at age 45, Archer is the author of a string of bestselling pulp novels, including "Kane and Abel" and "The Prodigal Daughter," whose trans-Atlantic success has made him a multimillionaire. A man of boyish good looks, endless energy and wisecracking charm, he has become equally popular on the lecture circuit and as a game show participant.

After churning out six books in nine years, Archer has returned to his first love, politics. Last fall, Prime Minister Margaret Thatcher named him deputy chairman of her Conservative Party in a major reshuffle designed to inject flagging Tory fortunes with new glamor and vitality in the preparations for the next general election.

As new party chairman Norman Tebbit put it, "Jeffrey will bring a touch of dash and style" to the staid Conservative ranks. Among the pinstripes and frown lines of the party hierarchy, none but Archer received an invitation to judge last November's Miss World contest.

Tebbit was to be the brains of the new party profile, plotting political strategy, streamlining Conservative headquarters and publicly pointing out the foibles of the opposition Labor Party. At a time when the Conservatives occasionally were running last in opinion polls, Archer's task was to rally the grass roots, pepping up Tories who the government fears have grown apathetic, or even doubtful, after 6 1/2 years of Thatcher.

In some political cultures, Thatcher's choice might have been considered a stroke of brilliance. Archer was not only a recognized crowd drawer, he also had Conservative political credentials. After graduation from Oxford and early success in business, he was elected the youngest member of Parliament ever at 29, and served five years.

When an unwise investment went bad and he was driven close to bankruptcy, Archer abruptly resigned his seat. Voluntary political retirement ultimately worked to his advantage, as he was credited with having done the honorable thing and quickly remade his life in an entirely new field as a phenomenally successful writer.

Four of his books have ended up on the New York Times bestseller list, three of them at No. 1. "Kane and Abel" sold 3 million copies in its U.S. paperback edition, and was made into a television miniseries shown on CBS.

But one man's dash can be another's disaster, and initial reviews were that Thatcher had made an inexplicable blunder. For many in the upper Tory echelon and those who aspire to it, glamor and celebrity are to be disdained, and self-made money is nearly as embarrassing as no money at all.

"Mr. Archer undoubtedly has charm, energy, acuteness and talent," noted Peter Riddell, the respected political editor of the Financial Times. "But his liking for self-promotion and his history do not appeal to more conventional politicians. To them, he is rather too flashy, rootless and smooth, lacking any real political substance."

The Spectator, an often crotchety conservative weekly, was more cruel. Archer, it observed, "has the integrity of the wholly plastic, seeming ultimately indifferent to all questions save whether the Perrier is properly chilled and why he failed to spot the chicken-sexer on 'What's My Line.' "

For the Labor opposition, Archer has presented a golden opportunity to attack Thatcher's much-reported belief that Tory problems -- high unemployment, ragged government services and a reputation for not caring much about either -- were more a question of "presentation" than substance.

Conservative chairman Tebbit, said Labor leader Neil Kinnock, was going to have to explain the "paradoxes, the inconsistencies, the hypocrisies" of Thatcherism. "No wonder he's been given a professional fiction writer as his deputy chairman."

Barely a month into his new assignment, Archer stumbled. Expounding his own views about Britain's 13.5 percent unemployment rate, Archer told a radio interviewer that one reason a lot of people had no jobs is because they wouldn't get off their "backsides" to look for work.

Three days later, in a published interview in which he complained about poor presentation of government policies, Archer was quoted as cracking, "You wouldn't buy a used car from this government, would you?"

Although Archer already dominated the headlines, there was more to come. At a crucial point in talks leading to the signing of the recent Anglo-Irish agreement on Northern Ireland, Archer called the deal "impracticable" since the Protestant majority in the north would never accept an arrangement with the participation of the Catholic Irish Republic to the south.

In a remark apparently meant to be humorous, he speculated on the radio about the taboo subject of a reunited Ireland, and suggested that hard-line Protestant leader Ian Paisley might like to be prime minister of it.

"What a Wally," headlined a Belfast newspaper, using a slang word meaning approximately "jerk."

"I've apologized every day since," Archer said in an interview, referring to the "backsides" remark. "And if you'd like me to apologize to you, I'll apologize as well."

This interview was conducted in Archer's automobile, as he drove himself across the British Midlands on a recent one-day barnstorming trip that included speeches in three cities. He spends at least three days of most weeks on similar trips, leaving his university professor wife and two sons at home outside Cambridge.

"I have two major jobs," Archer said. "One is to rally the party faithful. Because, there they are, working out in the sticks, in the rain, pretty fed up."

He pointed out, "We're coming up to an election" that political analysts say may be as early as spring 1987.

The second part of the job, he said, is "to listen when they whisper in your ear, 'we don't like this,' or 'we don't like that.' " In Birmingham, Nottingham and Sheffield, his venues for this day, he found that Conservatives care about law and order. They are concerned about the violence at soccer games, and the violence in Britain's inner cities.

"In Scotland they want property tax rate reform . . . . In Wales, they all want this new bridge for the Severn River . . . . Unemployment is one that's regularly on their lips," even though it may affect few in his audience. "In many cases it's because they feel guilty . . . in our country there's a sort of in-built guilt about such things."

The Midlands, Britain's industrial heartland where unemployment is high and prospects dim, is largely Labor country and Archer's message is likely to fall on deaf, if not hostile, ears. Yet, in Birmingham, a hardy band of 400 Conservatives, the Calthorpe Women's Luncheon Club's largest turnout ever, showed up to listen to him.

He started with a string of jokes, most of them at his own expense. He was first elected to public office, he said, while working in journalism for the British Broadcasting Corp.

"I wanted to be prime minister. They weren't surprised. Half of them wanted to be prime minister, too."

His delivery was loud and staccato, half carnival barker, half television quiz show host. After listing the accomplishments of the Thatcher government, and the dangers of a return to socialism with Labor, Archer came to the pitch: "The prime minister cannot do it on her own . . . . I appoint each and every single one of you in this room deputy deputy chairman of the Conservative Party. Because we need every one of you."

In the lobby outside, a table was piled high with Archer paperbacks, a commercial offering that caused some raised eyebrows. Far from sounding chagrined, Archer loudly insisted that the volumes be sold for 3 pounds each, rather than the cover price of 2.25, since "it all goes to the party."

Archer's attributes clearly distinguish him from many of his fellow politicians. What was it about him that appealed to Thatcher?

"Well, I'm available." He laughed. "I'm enthusiastic." He laughed again. And, although "I don't want you to put this in my words," both Archer and Thatcher are aware that, for reasons that have little to do with politics, people will come to listen to him.

Describing himself as a social liberal and a fiscal conservative, he said he became "turned on to politics" at Oxford.

From Oxford, he went to the BBC, then went into business on his own. Then came Parliament, and then disaster. On the advice of a friend, he invested $1 million in a company called Aquablast, a product and procedure to clean the outside of high-rise buildings. The story is a complicated one, but the scam perpetrated on him was similar to the one on which the plot of Archer's first book, "Not a Penny More, Not a Penny Less," is based. Overnight, he was $1 million in debt.

"You can either go bankrupt, and just call a day and pay a penny on the pound, or you can get down to it. I realized then, or rather my friends told me very clearly, that if I went bankrupt, then I could never return to public life in any form."

Rather than declare bankruptcy, he resigned his seat in Parliament, set up a schedule to begin to repay his bank, and thought about how to get the money to do it. He had never written before, but started "more out of desperation . . . to be doing something or go berserk," since "only a very stupid person" could hope to get rich from novels.

The rest is more or less history.

"Not a Penny More, Not a Penny Less" was a hit, followed quickly by the blockbuster "Kane and Abel," of which he says, "It's no secret, it was openly auctioned in New York, and the paperback rights went for $2.2 million."

Once the next election is over, Archer said he will go back to writing, at least for a while.

"But I shan't write on politics again. I will never write on politics again. It's good material . . . but I've written one political novel, and my next novel is going to be on the art world."