LIKE PROFESSIONAL SPORTS, political campaigns end in a championship competition. But unlike the baseball season, for example, which offers 162 direct clashes even before the playoffs, long campaign seasons provide few head-to-head confrontations allowing fans the opportunity to cheer and pundits the occasion to analyze. As a result, any joust short of actual balloting receives an inordinate amount of attention. This is especially so for debates.

Most respected political analysts agree that the series of debates in 1960 between John F. Kennedy '40 and Richard M. Nixon cemented in the public's mind the images of a forceful, intelligent Kennedy and a shifty, unattractive Nixon. Gerald R. Ford, with his Poland-is-free gaffe in 1976, significantly damaged his respectability, weakening his campaign. Jimmy Carter avoided injury during the 1980 primaries by refusing to debate Sen. Edward M. Kennedy '54 (DMass). Yet he did himself in, many say, by squaring off with Ronald Reagan one week before the general election. The lasting impressions of that session were that Reagan was kind and gentle, concerned whether the voters were "better off now than you were four years ago," while Carter was nasty and brutish.

For Massachusetts residents, add to that list the August 1978 gubernatorial debate, featuring then-Gov. Michael S. Dukakis, then-Director of the MassPort Authority Edward J. King and then-Cambridge Mayor Barbara Ackerman. Quite possibly, that hour-long discussion, more than anything, transformed King from a weak challenger to a clear and viable alternative.

During that decisive confrontation, King, taking advantage of the awkward format, ignored questions and his opponents remarks and used the opportunity to contrast himself' with the incumbent not only in substance but in style. He repeatedly ran through his checklist of issues, stating his support for capital punishment, a higher drinking age, limitations on government growth and his opposition to state funding for abortion. He did so, like a broken record, not only in his opening statement, but in response to practically every question asked, including those dealing with Kennedy's potential presidential candidacy. Ackerman's political leanings, and prison rehabilitation.

Dukakis, on the other hand, tried to answer the questions directly but made the mistake of ignoring his opponent. He came across as evasive. King came off looking simplistic to some but strong and assertive to many. And no one could come away not knowing where King stood.

This Tuesday, Dukakis, again leading in the polls by a wide margin, faces King for a rematch Lt. Gov. Thomas P. O'Neill III, the third participant, will fight to take some of the support, or at least some of the attention, from the two main attractions. Despite some similarities, comparisons between this year's contest and the debate four years ago cannot be carried too far because of fundamental differences in the structure of the debate and the political circumstances of the candidates.

One seemingly mundane, but potentially important contrast, lies in the ground rules. Last time, a reporter addressed a question to one candidate, and the others responded in turn. This loose format, made more ridiculous by queries tailored to only one candidate, favored the contestant who could avoid the questions rather than answer them. This time around, reporters will question one candidate at a time, with no response from the others. The section set aside for candidates to question each other should also better establish a contrast.

Timing this year is also key. The 1978 debate was held the week before Labor Day, only a couple weeks before the September primary. The April date allows sufficient time for King or Dukakis to recover from a poor performance. O'Neill must make a strong impression merely to preserve his campaign. The debate takes place just before the state Democratic convention, which will make a non-binding endorsement for governor. Dukakis is already assured an overwhelming victory, (the delegates having been committed in early February caucuses), which may counter a strong showing in the debate by King.

The main difference, though, is the role reversal between Dukakis and King. King probably would never have consented to this showdown if he were even close in the polls because debates historically have worked against incumbents. Dukakis' political sense should have told him to avoid a direct confrontation four years ago. Now, as a challenger with a large lead in the polls and with no current record to defend, he is sitting in the catbird's seat.

KING IS NOW vulnerable to the same challenges he fired so righteously at Dukakis last time. "I favor limiting taxation, a Proposition 13." King told viewers, but he opposed Proposition 2 1/2 when it reached the ballot and has added to the tax burden by imposing high fees. He harped on the increases in crime under the Dukakis administration, yet, the most recent federal statistics show that crime in Massachusetts is still going up and that Boston is still the most dangerous city in the nation.

In 1978, King effectively used the power of the challenger in exposing what he felt were the failures of the Dukakis administration. This year, the names are the same but the situation has changed. And King may find that it is the incumbent and not Dukakis, who is vulnerable to attack.