ONE OF THE best-concealed secrets of the current political season -- a secret that has escaped the notice of politicians, pundits and, to date, voters -- is that Edward M. Kennedy's drive for the White House has virtually all the elements of a successful political campaign.

This suggestions may sound like pure poppycock to anyone who has watched Kennedy, after entering the race at the top last fall, set new records for the political men's downhill ever since. And it is open to the perfectly accurate gibe that the only element Kennedy's campaign lacks is votes.

Fair enough. It is indeed difficult to think of a realistic scenario under which Kennedy could still win the Democratic presidential nomination, and if he doesn't score a sizable victory in his own state of Massachusetts on Tuesday, all bets will be off. But change is a constant in politics, and if fortunes change and Kennedy starts to win, all the "experts" who now say his cause is hopeless will start explaining that the underlying reasons for a Kennedy victory were in place all along. And they will be right.

Whatever his earlier problems, Kennedy's campaign right now is based on a favorable conjunction of candidate, issues and vulnerable opponent. That is, Kennedy today is a forceful campaigner who has positioned himself on the popular side of the central economic issue, who clearly has his opponent on the defense on pocketbook questions.

Kennedy's campaign does have some minor handicaps, of course, little things like lack of money, unsatisfactory advertising, fragile staff morale and internal staff rivalries. But these are the kinds of problems that will disappear with the first sign of a victory or, in Kennedy's case, near-victory.

And then Kennedy has a major problem -- the strong strain of anti-Kennedy sentiment in the electroate, a sentiment crystallized in the word "Chappaquiddick." This may be insurmountable; but then again it may not. It is worth noting here that Ronald Reagan's age problem was also widely described as "insurmountable" -- until Reagan won big last Tuesday, consigning the "age issue" to the dustbin of punditry.

Before we examine Kennedy's problems in detail, though, it is important to look at the three major assets of his campaign - assets that normally add up to victory.

The Candidate.After three months of stammering, tongue-tied, uncertain performances across the country, candidate Kennedy has finally gotten his act together. These days he delivers, most of the time, clear, lively speeches that receive, most of the time, warm responses from his audiences (and, as a Kennedy, he always draws big audiences).

Kennedy still falls into occasional slips of the tongue. In a speech in Gorham, N.H. -- a speech he began with the salutation "My fellow friends" -- Kennedy said he was "looking forward to the day when the members of the hostages will be returned to their families." The traveling press corps howled, but the audience didn't seem to notice. And the gaffe was not reported very much, partly because the press now considers Kennedy's slips to be an old story and partly because many reporters have decided it is unfair to zap Kennedy for the kind of mistakes that every candidate makes now and then.

Candidate Kennedy has also demonstrated a striking personal resilience during his calamitous campaign. He has reacted philosophically to the reversals he has experienced and managed to come out swinging after each defeat.

The day after he took a solid licking in New Hampshire, for example, Kennedy, shrugging off fatigue and a persistent cold, put in a 15-hour day that ended with a booming speech to a big crowd in Montgomery, Ala. "The president who was going to cure inflation . . . has given us 20 percent inflation and the highest interest rates since the Civil War," Kennedy shouted. "Those are statistics, but they are measured in human terms. They are measured in the lost dreams of young couples who cannot buy a home, in the lost dreams of . . . seniors who are told by their president they have to shiver in their homes on a winter night for the good of their country.

"Yes, yes!" the audience called out. "Right on, brother!"

There is a strain of political though that holds that Kennedy's heart is not in the presidential race, but most of those who put forward this idea have not spent much time with Kennedy.

Noen of the heart's-not-in-it theorists were along, for example, on Jan. 18, when Kennedy left Washington before dawn, put in five stops in Iowa, flew to Indianapolis for a late-night fund-raiser, and then proceeded to Preque Isle, Maine, where he got three hours' sleep before another long campaign day. Other than masochism, there is no explanation for such a schedule but a zeal to win.

Kennedy is telling advisers today that he intends to stay in the presidential race all the way, even if it means that, like Rep. Morris K. Udall of Arizona in 1976, his sole role at the Democratic convention is to turn over a few hundred delegates to a victorious Jimmy Carter. But if Carter cannot do something about the economy by then, Kennedy's position at the convention may be much more important than that.

The Issue. For the first three months of his campaign, Kennedy flailed around on a sprawling spectrum of issues ranging from who-shot-John-in-Tehran to the wiretap provisions of the criminal code bill. But now his campaign has a focus. To the extent that this campaign will turn on issues, polls show that inflation will be the chief one. And Kennedy today is the only candidate who offers a clear solution -- an immediate freeze on wages, prices, profits, dividends and rents.

Sure, this is Richard Nixon's position, and, sure, every other candidate says it can't possibly work. But the people who like Kennedy's solution are the people -- about 65 percent of the American people, according to recent polls. To the remaining 35 percent Kennedy can point out -- as he does every day now -- that economists and columnists from right to left have now endorsed the idea.

Regardless of its economic worth, Kennedy's support of controls has been a priceless political gem. He now has an answer when he is asked, as every candidate is asked every day, what he would do about inflation. "There are really only two choice," he says. "You might not like them, but that's all you have -- either an indefinite period of inflation out of control or an immediate freeze." The audience reaction is not euphoric -- but it has grown visibly more enthusaistic since last Friday's inflation figures came out.

The polls suggest that most people disagree with Kennedy's other major domestic proposal -- a call for immediate gas rationing. But he has gotten a notably positive reception nearly every time he has raised the issue because of the context in which he brings it up. Noting that the "Carter Doctrine" might require U.S. troops to protect Mideast oil supplies, Kennedy says, "I think the American people would rather do with a little less gasoline than spill American blood to protect OPEC's pipelines." Loud applause and cheers usually follow.

Two other issues Kennedy is hitting hard -- opposition to nuclear energy and his criticism of Carter's call for draft registration -- apparently are minority positions within the electroate as a whole. But they are the kinds of issues that stir liberals to pull out their checkbooks and spend their weekends ringing doorbells.

Moreover, Kennedy is clearly in the majority, according to opinion surveys, on the issue he loves most -- his call for a comprehensive federal health insurance system. No matter how flat he is in any given speech, he invariably comes to life when he gets around to talking about health care.

"Somewhere tonight a sick child will cry in the night," he says, "and his mother will lie in bed worrying whether her baby is $50 or $75 sick -- because she has to find that money to get him treatment. Somewhere an elderly couple is living in fear -- fear that some accident or illness will use up every penny they have saved. And our society ought to put some value on freeing people from that fear." Some of his sentences are never finished because they are drowned out by a roar from his audience.

The Opponent. Candidate Jimmy Carter said in 1976 that the "terrible, unacceptable" inflation rate then -- 6 percent -- was due to Republican "mismanagement." Carter would bring it down, "and you can depend on it." Under Carter's management, the inflation rate has tripled. This is a vulnerable incumbent.

As has been widely noted, Carter's remarkable success so far in the 1980 campaign stems largely from the nation rallying round the president in a time of foreign crises -- crises which have distracted attention from economic troubles. But when the focus shifts back, Kennedy will have Carter in a box. Since Jimmy Carter steadfastly refuses to employ Kennedy's solution, mandatory controls, there is not much more he can do about inflation beyond cut federal spending on social programs.That will not endear him to liberal Democratic canstituencies.

Carter's biggest political advantage is that people like him and sympathize with him. But the president is least likeable and least sympathetic when he is on the defensive. He demonstrated that last week when he was challenged about his economic policies and the unprecedented inflation and interest rates they have helped spawn. Those policies "suit me fine," the president snapped, automatically creating a free-fire zone for editorial writers, cartoonists and opponents in both parties -- including Kennedy.

The Problems. Kennedy's campaign is beset with the types of problems that crop up in any losing effort. The most acute right now is probably campaign money. Kennedy's campaign treasury is up against it, and no amount of bravado from the campaign headquarters can conceal that truth.

But Kennedy, more than any other politician in the country, can get by for a while on limited funds. He is, after all, the last of the Kennedy brothers, a real-life celebrity, and is assured generous media coverage everywhere he goes. If the reporters who greet him at every airport ask about economic issues (and they have done so recently), and if he can give a reasonably conherent answer (he has done so most of the time recently), he is almost guaranteed the equivalent of a free advertisement on the nightly news in every town he visits.

Rationalizing away Kennedy's fundamental problem -- the combination of cheating, Chappaquiddick and marital problems that wrap into the character question -- is considerably more difficult. Polls show that negative feelings toward Kennedy are growing each month, and that nearly half the Democrats nationwide have an "unfavorable" view of him.

But the polls are as changeable here as they are on every other issue. In a CBS/New York Times poll last November, twice as many Democrats had "unfavorable" views of Carter than of Kennedy. The positions have reversed in three months. Who is to say they won't reverse again?

In summary, not many candidates would volunteer to be in Kennedy's position right now -- a decided underdog whose chances are all but written off by the leading political savants. But a great many campaign managers would like to have the combination of candidate, issue and opponent that Kennedy's campaign boasts right now. Considering those assets, and the ephemeral nature of some of his problems, it is still quite possible for Kennedy to win his party's nomination this year.

If it happens, the pundits can hang their heads and bow to a tweedy Boston matron whom Kennedy met while campaigning the other day at the Harvard club. "Oh, Ted," she said in her best Back Bay accent, "I'm convinced you're going to whip his ahss."