PRESIDENTIAL DEBATES don't exist. Instead, candidates agree to joint press conferences where they can answer (or sidestep) predictable and predigested questions. In these "debates" the candidates simply restate party platforms. Even the media panelists realize this sad state of affairs; they meekly protest, adding, "And could you please state specifics" to their questions.

Suggestions have been raised recently that would alter the style of presidential elections. They include shortening the primary season, changing the locations and timing of primaries, even turning to a one-term presidency. A less dramatic measure that might add structure to the campaign would change the style of "debate," forcing a more comprehensive discussion of particular issues.

The basis of debate is argument. But this quality was strangely missing in the Reagan-Anderson debates of last month and the Carter-Ford debates of 1976. The problem lies in the fact that we depend on a panel of journalists to prod the candidates into discussion. No journalists should be present at Presidential debates. We should let the candidates tell each other when they are hypocritical, inaccurate or misleading.

Let the candidates not only state their positions but defend them, and defend them directly against the alternatives of their opponents. Candidates should address answers to each other, knowing they will be challenged, rather than to a TV camera.

Direct questioning will lead to the exhaustive discussions of flip statements that pass by on the campaign trail without follow-up. (Take a simple and straightforward example like Reagan's plan to raise the national speed limit from 55 mph. When questioned, Reagan replies that the national government shouldn't dictate its citizens' style of living. At a debate a Reagan opponent could quote Department of Transportation statistics: a higher speed limit would mean more traffic deaths and more wasted fuel.) Discussions of issues such as the 55 mph speed limit have not been avoided this campaign. But the repercussions of suggested solutions are rarely addressed honestly. Argumentative debate would allow such discussions.

Candidate-to-candidate questioning serves three purposes: First, it will make it harder for candidates to escape with the amorphous answers often given. Candidates will be forced to answers questions with which they are uncomfortable. Second, it will push candidates to educate themselves completely on the entire range of matters relevant to a President. Third and most importantly, such a format will reveal how candidates react under pressure.

The emphasis here is on debate. A nonpartisan moderator (possibly a journalist) will serve only to limit the length of statements and maintain some degree of order. After an opening statement by each of the participants, personal confrontation will move the discussion.

In order to see full discussions of single issues rather than initial questions followed by innuendos, each debate should focus on a single topic. A series of consecutive debates on inflation, SALT II, unemployment, and increasing productivity would allow adequate preparation and presentation. The topics could be flexible with changing circumstances.

UNDER THE PRESENT ELECTION laws, we can't "force" candidates to debate. Candidates adopt various reasons for opting out. Some cite national security reasons, others discomfort with the agenda or timetable, and still others worry about who will be included. Most often, one candidate will have more to lose by debating than his opponents.

But how can we arrange regular debates with each election? There are two methods. One would somehow entice candidates to debate. This might be accomplished by an independent election agency raising "debate" funds to be given only to those candidates who participate. Federal campaign laws would be changed to accomodate a "debate clause." These funds would then be used by the candidate during the campaign for whatever purpose he wished. Only a fat check would effectively attract any candidates. Still, even a reasonable sum would not attract a candidate who really believed he would lose a substantial number of votes by participating.

A more unusual but effective way of engaging debates is simply to legislate them. That is, add to the election laws a stipulation that candidates must participate in scheduled debates in order to qualify for matching funds.

Of course, setting such contingencies for presidential campaigns is a dangerous precedent. Where would the contingencies stop? Should we really be telling candidates what to do? What's to stop us from making campaign funds contingent on a campaign visit to the South Bronx? To set a debate stipulation, we must be sure we consider it of utmost importance. Will debate enrich the elective process?

One might argue that such a system does not necessarily select the most forceful leader or best White House manager but only the best debater. But this objection must be seen in the light of the present system. Many believe that today's electoral process only helps us select the best campaigner with the best advertising director. With this in mind, regular and organized debates are the best showcase for voters, especially debates in the style of argument put forth above. No one can predict who will serve a strong four-year term. But with debates, we will see our candidates think. We will see them not only restate positions, but defend them as they have to for four years. Eloquence is not always the critical factor in debate. Thoughtfulness, pursuit, attitude all contribute to the performance and its effect. The best speaker will not always win.