Gary Hart as president

IT'S not too early to assert, with considerable conviction, that if Gary Hart can continue to project a John F. Kennedy image - and not evoke memories of George McGovern - he could win both the nomination and the presidency.

As a president Mr. Hart would, potentially, possess these assets:

* If he should defeat Reagan, he will do so only by convincing the majority of voters that he is, indeed, the candidate of the future. And in so doing he will have made Reagan - as he has, thus far, made Mondale - the candidate of the past.

Thus, for a while, Hart would have a mandate for carrying the nation forward. He would, like Kennedy, be a symbol of moving ahead. It would be his moment to implement the new ideas he is talking about, most of which he has yet to unveil.

* As a president in the Kennedy tradition and with Kennedy's ''tomorrow'' look, Hart should be in a position to bring in the best and brightest from the academic community, as both Franklin D. Roosevelt and John F. Kennedy did, to shape his ''agenda of the future.'' It could be a particularly lively period in presidential history.

* He seems to possess the mental flexibility to move to the center on vital issues - where Kennedy was able to put himself in both the campaign and after reaching the White House. Kennedy was able to prove in that first debate with Nixon that he was a reasonable and prudent person who took moderate views for the most part.

Up to that point most Americans were a bit frightened about what the Massachusetts senator might do in the presidency, thinking he might be a somewhat erratic servant of leftist ideology. Kennedy's performance in debate quieted those fears.

Later - some of his critics' evaluations to the contrary - Kennedy was pretty much in the center, ideologically, enough so as to command the broad public support a president must have to lead. Hart may be positioned to do the same.

Like most Americans, Hart is for a strong defense. He merely feels that there are better ways to get ''more bang for a buck,'' ways that would open opportunities for big spending cuts.

His position on dealing with the Soviets has been detailed three times in recent months, but it doesn't go much beyond President Reagan's policy. He, too, is not ready for a nuclear freeze.

Hart feels that some concessions must be made by the Soviets. He doubtless would, from the outset, be reasonable and not belligerent in talking to Soviet leaders. And he might be willing to take a little less from the Russians in return for a deal.

What, then, would be Hart's deficits?

* He was once George McGovern's right-hand man. McGovern is an honest, idealistic man who carried a cause valiantly on his shoulders. But he represented a passionate minority which tended to push all other Americans into Richard Nixon's camp. Thus Nixon won by a crashing landslide, shaped by the relatively narrow appeal of the McGovern campaign.

Hart has reshaped himself since that time. He moved a long distance to the right as he won his Colorado Senate seat. He remained a liberal in the eyes of his critics, but has traveled away from his McGovern days, when he identified closely with the youth protests of that day.

Hart will say he revised his point of view because of new circumstances. And a leader must be able to do that. But there remains a question: Does Hart retailor his positions to get elected? Is there something of the opportunist in Hart?

The voter anxieties raised over his changing his name and, perhaps, fiddling with his age tend to support the theory that his campaign may yet come apart because of further disclosures that will underscore the question: When is Gary Hart really Gary Hart?''

* Finally, Hart was the man Bt the controls of the McGovern campaign, which was a political disaster. A certain amount of political ''history'' is now being written that says he performed brilliantly in that role. Untrue.

The political strategy, much of it coming from Hart, just didn't pass the test. And for the haphazard campaign that was waged - with McGovern often improvising a trip that would cause costly backtracking - Hart has to be blamed as well as the candidate. Whatever else, Hart did not prove himself to be a good administrator.

There is nothing in his record, in fact, that could convince the public that Hart would be a strong man at the controls of the presidency. His ability to throw a heavy ax and hit a target, as politically potent as the picture was, does not really tell us whether Hart would, like Kennedy, be a president who was in command.