A few days ago J. Kearney Shanahan, attorney-at-law, Cleveland, wrote a letter to Washington. He told Timothy Kraft, President Carter's campaign manager, speaking as a Princeton graduate to a Dartmouth one, as he put it, that he wanted to volunteer his services in the forthcoming year.

"In the interest of a candid and fruitful discussion," he wrote, "I would suggest meeting for dinner on the evening of Nov. 5th or 6th. If there seems to be a fit between your needs and my interests following dinner, I can stay over till the next day to meet with anybody else you think appropriate."

Shannon was doing nothing improper, and this is no expose. He is merely one of thousands of people, in Washington and out, clamoring for a chance in the campaign. Shanahan, though, happens to be more candid than most about why he wants in.

First, he says you have to take into account his own ego and ambition. "I don't think there's a free lunch, and I don't believe in blind altruism." Besides, he adds, his law firm made a conscious decision "to get one of us -- probably me -- into a position in Washington" during the presidential campaign. It would be "valuable to our pedigree" and add credibility among their prospective clients to have served in Washington and then return with greater personal aquaintances among important political people.

Offering his services to Carter was equally calculated. "That gets down to the basic Machiavellian nature of it," he explains. "I think -- I know -- Kennedy's not lacking for talent. He's got a long line of talented people already lined up outside his door.So it comes down to a question of how much difference I can make and what would be the dividend.

"I think Carter's looking for all he can get, and if he pulls it out he could be a grateful guy. I've got to look at it from a cost benefit analysis of what I get out of it. Look, let's not kid ourselves, everybody looks at that way unless he's doing it for emotional reasons."

Whether J. Kearney Shanahan comes to Washington, gets that advantageous position for himself and his firm, and makes a difference for Jimmy Carter and his campaign, matters not in the larger context of this story. As his celebrated fellow Princeton alumnus, Scott Fitzgerald, once said, "Start with an individual and I'll show you a type," and Shanahan is very much a political type, instantly familiar to countless operatives dealing with the flood of applicants, young and old, battle-scarred and untested, hardeyed and dreamy, now seeking a spot -- almost any spot -- inside the campaign.

The phones that are ringing in Washington these days, and the lines that are forming outside the campaign headquarters, are visible reminders of a familiar fact.

Americans may be, in the vernacular, turned off on politics, weary about candidates and their promises, and cynical about the campaign. But the political industry of Washington, and thus the nation, that fuels the campaign, gives it direction and focus, form and substance, remains boisterously, vigorously alive.

"We're a little like Britain," says Peter D. Hart, one of Washington's most respected political consultants, "in that we have a shadow government and shadow practitioners of politics."

Lest there be any doubts about the existence of either side of this political reality, the scene at Kennedy campaign headquarters these days should prove Hart's point. There, in that reconverted Cadillac showroom, can be seen the veterans of campaigns past -- those who served in the previous Kennedy efforts, or on the trail with McCarthy, McGovern, Muskie, Church, Udall and others half-rememberd or entirely forgotten. They are either on board or seeking admittance, thereby proving another point made by Hart.

"This is a town which always smells a winner," he says (or thinks it does, not always correctly), "and so they say, "this is my chance to be in on the ground floor.' It's not exactly a profile in courage."

The third Kennedy and his campaign have attracted, understandably, an unusually large number of applicants -- probably the greatest for any presidential effort in at least a decade. But that turnout obscures the larger dimensions of the permanent political industry already in place. It's a small industry that spends great sums and exerts even greater influence over how America is governed and by whom.

"If you think about a presidential compaign, you're describing an institutional unlike any other in our society," says Mark Shields, who has managed many a campaign from Washington over the years before becoming a journalist. "You're putting together an operation that involves hundreds if not thousands of people, paid and unpaid, that will raise and spend millions of dollars over an intensive period of some 18 months, and then will go out of existence. If you and I wanted to go into the Dairy Queen or disco business, we'd want to talk to somebody who had done it before. You need that expertise. It's the same with politicians. They want somebody with expertise, somebody they can trust."

So they turn to the Peter Harts, the Pat Caddells, the Matt Reeses and the other politicals consultants of Washington, proven in national campaigns past, and the media experts and strategists like the Charles Guggenhims and Gerald Rafshoons and David Garths, each decorated with ribbons from victorious forays in previous years.

The political business has grown enormously over the last decade, and, as Matt Reese says, "I expect to see it 10,000 times greater in another 10 years." Reese himself is a case in point. When he started his Washington political consulting firm in 1966, there were only four or five people doing similar national work in the field. Today there are hundreds, offering services at all levels from the presidential race down to city and county contests. Reese heads a permanent staff in Washington, assisted by some 20 people who do work for him regularly throughout the country.

"I get four or five applicants a week, every week of the year," he says. "They include the pick of the cum laude crop from the Ivy League." Some are willing to work for nothing as interns, an entry into the professional political world.

And now Reese, like the others, finds his phone ringing from around the country (and Canada) from those who want a chance at the biggest political race of all -- the presidency.

Why anyone wishes to enter an artificial world, filled with tension and exhausting hours of work, often unnoticed and unrewarded, remains a subject probably more fit for the novelists or screenwriter than the journalistic scribbler. Lives are disrupted, family relations strained, nerves and tempers frayed, resources both corporate and personal depleted (it's quite possible at least a billion dollars will be spent electing a president during this next long year), but they do -- and in ever greater numbers.

Young political consultants and aging political correspondents, and political veterans, the innocent and the jaded alike eagerly vie for a place in the campaign, a place they fight to hold for month after grueling month.

"An awful lot of people go into it saying, 'Where is the most fun, where is the most gain,'" says Susan Morrison, press cooridinator for George Bush's presidential campaign.

"I think it gives people a feeling of self-importance, a feeling of involvement. It's a feeling of the world knowing who I am. It's a piece of the action, a belief you can make a difference, but it's also power -- having access to people who have power."

Morrison herself is an example of the political industry, particularly as practiced in Washington. In 1972, after college, she covered the Indiana presidential primary as a reporter for a local paper there. She moved on to New York, worked briefly in television, and married Martin Plissner, CBS' political editor, and then came to Washington. In the 1976 campaign she worked as a field director of Frank Church's attempt to win the Democratic nomination. He lost, and she became a political researcher for David S. Broder, The Washingotn Post's political columnist. She left The Post to work for the Democratic National Committed (and the fortunes of Jimmy Carter) and next switched to the Republican Bush's presidential campaign.

"I am going to end up at three or four parties this weekend," she said the other day, "and I can tell you I'll see the same people every night." That is, she'll see the same kinds of political people, whether pollsters, consultants, or members of the Washington political press corps. "Why do I do it? I do it because it's important, because I should not miss a chance to tell them why the train is leaving on George Bush, for instance, or to pick up what other kind of information I can."

She's on the inside, and now she also fields requests from those outside who want in.

There's probably no real common denominator to them, but let's take the example of two people, both of whom are hoping for positions with Kennedy. The first is a congressional aide. He's been on Capitol Hill for five years and has had it with that side of Washington. "I find the governmnent boring," he says, "and I want to get out of it. I was 13 in 1960 and I don't know about that campaign, but I'm a Kennedyphile. I am excited about this race. I was excited in 1968, but my emotion then was anger. People today want to be excited and turned on, and I think Kennedy can do it."

He's already had an important interview, and had been boosted in his hope-for shift by his congressional boss. Now, like countless others, he's waiting for word as to whether he'll be in.

Then there's Hal Wolff. He's been through it before, and is one of the legion of the survivors of the 60s. Wolff would like to recapture the feeling of exuberance he remembers during those early days when he came to Washington with the Kennedy administration. "The times haven't been so good since," he says.

Since March, Wolff has "been in a campaign mode." 'He was among those involved in the early efforts to create a draft-Kennedy movement. Now, because of that work and the belief he must have a special in, Wolff finds himself getting up to 50 calls a day from people who want a campaign slot -- here, or anywhere.

The irony is that Wolff himself in anxiously waiting for word that hasn't come. He wants a place in the campaign himself, and isn't assured of any. Now he confesses to feeling a certain paranola and frustration -- a feeling that the early workers may be those who are early discarded. He's prepared to give up his good job for a year and volunteer his services for a chance in the campaign.

"That's a $60,000 number for me," he says. "I can't think of anything else I'd spend $60,000 for, if I had that kind of money."

But then, as they all will recognize, the campaign isn't like anything else. It's more exciting than many a dull job and humdrum life. And certainly, as the people of Washington well know, this weekend one year before the election, campaigning is a lot more fun than governing.