RICHARD Nixon, in a taped television interview last Sunday, tossed out the idea that Sen. Edward Kennedy is still a powerful feature on the American political landscape. He made it sound as though the last of Joe Kennedy's four sons might be the dark horse of the Democratic convention this summer.
If the New York and Pennsylvania primaries had come out differently than they did - ''it'' could have happened. Suppose that Gary Hart had done well and Walter Mondale poorly. That would have meant the prospect of a close race between the two down to the wire, and that in turn could have led into a deadlocked convention.
In that case you could have written two equally interesting scenarios. One would be the convention stampeding for Senator Kennedy. Conventions have been stampeded. The classic example was William Jennings Bryan winning the Democratic nomination in 1896 with his famous ''Cross of Gold'' speech. It happened to the Republican convention of 1940 when Wendell Willkie took the nomination away from Tom Dewey.
It might have happened in 1960 when Adlai Stevenson made an unscheduled appearance at the Democratic convention the day before the nominations. The hall exploded. There was no doubt about where its heart lay. There was resentment over the pressure that the Kennedy machine had used in gaining a near majority of the delegates, and there was a deep affection for the man who had led them twice with dignity and honor against the unbeatable Dwight D. Eisenhower.
All Adlai Stevenson had to do in 1960 would have been to pass the word that ''if nominated I will run.'' I was in his hotel room at the last crucial moment when his best friends begged him to let them send that message to the convention hall. One final argument was that he should run to keep the presidency in Protestant hands.
That suggestion triggered the most eloquent and persuasive lecture I ever heard on religious tolerance. The radio brought in the counting of the ballots. The tide set in for John F. Kennedy. Adlai Stevenson was still preaching tolerance when the count went over the top for Kennedy. Adlai Stevenson seemed not to notice.
The alternate scenario for this coming Democratic convention in the event of a Hart-Mondale deadlock involves the Rev. Jesse Jackson. With a tie between the leading candidates the Jackson forces would hold the balance of power. They could make their choice between Gary Hart and Walter Mondale. They could command a high price for the votes that could swing the convention.
But then it isn't working out that way. New York and Pennsylvania did not go for Hart. They both went for Mondale, who now has more than half the total number of delegates he will need for the nomination (1,079 out of 1,967). His total to date is well over the combined total of 749 for Hart and Jackson together. So, the chances are that there will be no deadlock at the Democratic convention, that Walter Mondale will win without having to bargain with Jesse Jackson for the nomination, and without having to give the convention a chance to revive the Kennedy legend.
That reduces but does not eliminate the bargaining power of Jesse Jackson. If Walter Mondale is nominated, he will need every last black vote Jesse Jackson can persuade to come out on election day. Mr. Mondale proved in New York and Pennsylvania that when in a tight corner he can come out swinging. He showed a toughness in adversity which we had not seen in him before. Undoubtedly that had much to do with his win in those two crucial Eastern states. But getting the best of Gary Hart is one thing and Ronald Reagan is another.
Only two persons in the political running in the United States this year have a touch of that indefinable but priceless quality called charisma. Ronald Reagan is one. Jesse Jackson is the other. Whatever one may think about Jackson policies and behavior, he has a touch of that something that makes people listen to him speak even when they don't like what he is saying.
Jesse Jackson can rouse an audience as a Franklin Roosevelt or a John F. Kennedy could. He has brought to the voting polls thousands of blacks who otherwise would not be there. He and he alone can persuade or induce thousands of new black voters to come out on election day, if he chooses to do so. Walter Mondale can probably get the Democratic nomination without benefit of Jesse Jackson, but not the presidency.