Boston Celtics fans, of whom there are a great many hereabouts, got an extra bonus the other night during the telecast of the big game against Philadelphia: commercials promoting the presidential candidacies of John B. Anderson, Howard H. Baker Jr., Edmund G. (Jerry) Brown Jr. and George Bush.

These chilly February nights the television screens of New England are blossoming with political commercials. On some channels there will be as many as a dozen each evening during the coming weeks, thanks to the large number of candidates in the field and the hundreds of thousands of dollars they are willing to spend.

Interested voters will be able to learn something substantive about the candidates from their newspapers or television news, but if the surveys can be believed, most New Englanders' principal contact with these primary elections will come from brief encounters of the political kind: 30- and 60-second commercials.

This will mean judging George Bush, for example, on the basis of a 30-second spot depicting crowds enthusiastically cheering and chanting Bush's name while the candidate intones this message in a "voice over," talking as the cinema verite film continues:

"I've seen this country up close. I hear what Americans are saying. Yes, they want change. Yes, they want solutions.But they don't want yesterday's ideas promising everything to everybody. Americans today are ready to roll up their sleeves and rededicate this country to excellence, to principle, and to leadership from strength. And that's why I'm optimistic about our future."

According to the open files of Boston's major television stations, Bush will spend perhaps $150,000 on ads during January and February, just on the big Boston stations (whose signals penetrate populous southern New Hampshire.) He'll spend more on the Maine and New Hampshire stations. And he is not the biggest spender in the campaign.

By March 5 the world will know the winners in all of the New England contests -- the Maine caucuses and the New Hampshire and Massachussetts primaries. But after a brief inquiry here, the conclusion is irrestistible that the real winners will be three television stations in Boston. Each stands to earn hundreds of thousands of dollars in windfall revenues during what is usually the slowest advertising season of the year.

The federal election laws, the primary schedule and the booming growth of southern New Hampshire contribute to this windfall. This combination, together with the large number of candidates and their willingness to spend money, have given the 1980 presidential campaign a whiz-bang media sendoff.

The commercials being shown here, most of them just 30 seconds long, all slick and professional, seem significant on several levels: what they tell us about the messages the candidates want to convey; what they reveal about the financing or presidential campaigns; what they tell us about the television age in which we live.

A cynic might conclude that the messages are as varied as the candidates.In other words not much. In fact, the similarities can be striking.

Clearly, for example, the pollsters who often identify the voter concerns at which the media people then aim in the commercials have obviously agreed on the importance of "leadership" this year. Edward M. Kennedy promises leadership, and his ads carry the slogan: "Kennedy -- a time to take charge of the '80s." President Carter's ads promote "a solid man for a sensitive job." Bush promises repeatedly to lead, and his slogan is "A president we won't have to train." Baker and Brown pledge to be leaders. Ronald Reagan announced "All we need is leadership."

But there are also many differences among the several dozen commercials now being broadcast in New England, and even a few direct clashes. The meatiest involve Kennedy and Carter.

The Carter camp struck first with radio commercials directly attacking Kennedy, claiming that he did not live up to his campaign claims. "Whenever Sen. Kennedy paints his vision of the American future," each of five commercials began, "his record catches up with him."

For example, one Carter ad quotes Kennedy as saying he supported the Trident submarine. "The fact is that he voted to cut funds for the Trident by $885 million," an announcer says.

Kennedy has replied with radio ads of his own aimed directly at the president. One begins with Carter's voice, in an excerpt from last July's dramatic presidential address after the domestic summit at Camp David, when the president read aloud criticisms of himself.

"Mr. President, you're not leading this nation, you're just managing the government," Carter reads, quoting a letter from a southern governor. Kennedy then promises to do better.

The Kennedy camp has just completed new TV ads that also directly attack Carter. They have Kennedy looking earnestly into the camera and asking:

"Is it crisis or failure that keeps Jimmy Carter secluded in the White House? When we finally find out, it may be too late. Let's not allow that to happen."

Carter's television ads, prepared by his media adviser, Gerald Rafshoon, are strictly presidential, except perhaps for occasional tributes to Carter's skills as a father and husband.

Mostly the Rafshoon commercials show Carter in presidential poses, either at town meetings or in the White House. A typical ad has the president saying something about energy, then switches quickly to an announcer's voice, which says:

"You may not always agree with President Carter, but you'll never find yourself wondering whether he's telling the truth". Later the announcer ends with the commercial like this: "President Carter -- for the truth."

Brown's commercials include attacks on Carter without mentioning his name. In one of Brown's TV spots, all of which show him staring earnestly into the camera, every hair neatly in place, he says, "Either the president will continue to bumble away our national strength," or we'll get a new president who won't.

Brown may be the best television performer of this year's platoon of candidates. In one of his spots being broadcast here, he acknowledges that he has been accused of opportunism for his proposed constitutional amendment to balance the budget. In his ads, this is referred to as "a budget-balancing amendment," with no reference to the Constitution.

"A Democrat who favors a balanced budget may be unusual," Brown says, keeping constant eye contact with the camera, "But there's nothing opportunistic about living within our means . . ."

On the Republican side, much of the advertising sounds the same. Reagan and Bush have commercials with almost identical messages conveying their optimism about America's future. Most of the Republicans have similar ads committing themselves to strong national defense. Reagan's begins with film footage of the Nov. 7 military parade through Red Square in Moscow.

But there are also differences. Baker and Anderson, for example, emphasize specific proposals on the issues in their latest ads, whereas Reagan only touches on issues, and Bush avoids them entirely.

A Bush campaign aide, David Sparks, said Bush's polls showed that people were most concerned about "experience and leadership," so that's what the Bush commercials emphasize.

Reagan recently switched advertising agencies after deciding that his early ads were "too polished and flabby," as one aide put it. The new ones, done by Elliott Curson Advertising of Philadelphia, show Reagan talking into a camera, preaching his old-time conservative gospel. Reagan looks heavily made-up, but a campaign aide in Washington insists that this effect was created by lighting, not makeup.

The most dramatic Republican ads are Bush's, made by Robert Goodman of Baltimore. They contain music composed by Goodman that is reminiscent of "Victory at Sea," all strings and soaring trumpets.

In one five-minute ad that Bush uses for fund-raising, the picture shows crowds clapping and chanting rhythmically "We Want Bush!" The chants are audible behind Bush's raspy voice, sounding remarkably like Hubert H. Humphrey's, as the candidate says insistently: "We can solve absolutely any problem we want to, if we emphasize the fundamentals, if we stop wringing our hands about the failures of the past . . ."

Anderson's commercials are utterly different from those of his competitors, part of a purposeful attempt to advertise himself as a unique candidate. The spots include staged comments from people depicted as men and women on the street, followed by tart replies from the candidate.

In one, a young man says: "Bush, Baker, Reagan, Connally -- they all got the same ideas."

Anderson then comes on camera and says. "You're absolutely right. And I disagree with every single one of them on energy, women's rights, tax cuts . . ."

An announcer then adds, "Think about the Anderson difference."

Behind the commercials seen here in profusion every night lies a complicated system of time-buying and allocation by television stations.

Under the federal election law, stations must sell political candidates advertising time at their cheapest standard rates, what they usually charge their best advertisers, within 45 days of a primary. But the law does not require the sale of specific time periods, nor does it demand equal availability to all candidates. The rule is first come, first served.

The three major stations in Boston have slightly different policies for selling time to politicians. None of them, for instance, will sell commercial time within one of their regular news shows, but two of the three sell "news adjacencies," which the political media people covet. These are spots just before or after a news program.

The records of candidates' orders for time that each station must make available reveal some surprises. Anderson has contracted for about $200,000 in TV spots during the pre-New Hampshire period in Boston. Connally, who has raised about $9 million for his campaign but spent nearly all of it, has booked no ads for this month at the Boston stations. He is not making a major effort in the New England primaries.

The stations also allocate time availabilities outside the newscasts. For example, WNAC-TV, the CBS affiliate here, offered all the candidates one five-minute time slot and one half-hour time slot, but would sell no more of either category.

WCVB-TV, the ABC affiliate, Boston's top-rated station, limits candidates to two commercials per week in evening prime time, and has not offered any five- or 30-minute time slots. WBZ-TV, the NBC station here, allows a candidate no more than four ads per week adjacent to any of its four news programs.

The limitations can infuriate some political media makers, but most seem to have come to terms with them. The most obvious criticism, perhaps is that the standard 30-second spot offers no serious chance for substantive communication, yet that is what most politicians buy the most of on television.

All 30-second spots are not alike, however. On the ABC affiliate here, for example, they can be as cheap as $125, or as expensive as $9,000, during the winter Olympics later this month. Anderson, Baker, Bush and Reagan have all bought some time during the Olympics, Reagan quite a lot.

For the stations, a campaign like this one mens big money. At WCVB, the public files indicate, candidates have already bought $237,000 in commercials for February, and more can be expected.

Michael Volpe, the station's general sales manager, said in an interview that he was sure the commercials were effective. A 30-second political message does work, he said even if the idea is offensive.

In fact, Volpe said, "an ineffective candidate . . . could get elected" if his television commercials were sufficiently clever. A good citizen ought to study the issues and the candidates with some care, Volpe said, "but I'm afraid that's not the way it is."

And what is the effect on viewers of a dozen different political spots during one evening's viewing? Volpe had no ready answer to that, though he said he thought the large quantity of ads made their relative quality very important. "People remember the good $35,000, $50,000 commercials," Volpe said, referring to the production cost of a glossy 30- or 60-second spot.