The bartender at Sardi's, a soft-spoken fellow with a faint accent, got home to Jersey just in time to watch. He was impressed, but puzzled. "I was asking myself, where the hell have you been for the last six months?"

For Teddy, the answer -- and part of the problem -- is that it seems he's always been there.

In 1968, the anger and division of Chicago, the nomination was his for the taking. In 1972, in the raucous atmosphere of Miami as the clock struck 3 in the morning, his oratory swept the convention floor and diminished the luster of the party's new nominee, George McGovern. In 1976, in the wake of Watergate and the disintegration of the Republicans, the standard again was his to seize. In 1980, in the failure of the supposedly weakest president in memory, Jimmy Carter, Kennedy's decision finally to run meant the presidential race was over before it began.

And now, in the wreckage of his own candidacy, it is being said all over New York that in 1984, at the age of only 52, Edward M. Kennedy will be the man to beat.

With one more speech and one more moment on the stage, Teddy has redeemed his failures and resurrected his presidential hopes. Thus, at least, today's wisdom. The wisdom, of course, from us far-seeing pundits has been invariably wrong about Kennedy in the past and quite possibly will be in the future. But Kennedy's performance here seems likely to have a powerful effect on both his own future and his party's, short-term and long.

What Kennedy did Tuesday night in Madison Square Garden was deliver the best possible speech for Jimmy Carter, for the Democratic Party, and for himself. Whether it was the best speech of his career, as some are saying in the aftermath glow, is meaningless; his words 12 years before in St. Patrick's Cathedral here before his brother Bob's casket certainly had more emotional impact and eloquence.

But he gave a great political speech. It did more than transform a dispirited Democratic convention thick with the smell of discord and defeat. It is certain to carry weight in the presidential campaign that is about to start.

In a day when political parties are continuing to decline in public esteem and influence, he reminded the Democrats that they stood for the sum of all their disparate parts -- not just, as it has seemed in recent years, the constantly warring factions of one special group competing against another, with each canceling the other out. More important, he offered a prescription of why the Democrats have won national elections consistently for nearly half a century, and how they can do so again.

Kennedy was striking the sparks of what is left of the old coalation -- the unions, the blacks, the cities, the poor, the elderly along with the women -- and saying that together they still represent the majority. In terms of population, that clearly is true. Whether they continue to form a cohesive voting group any longer is highly debatable. But politically, the Democrats cannot win without them. There is where Kennedy's role in this campaign is most intriguing.

For Carter and the Democrats, the battleground of this campaign lies again in the major industrial states -- Massachusetts, New York, New Jersey, Pennsylvania, Ohio, Michigan, Illinois, California. With the exception of Illinois, which Carter won decisively, and Ohio, where he triumphed narrowly, Kennedy won them all in the primaries.

Carter, by every sounding, remains weak in them. They are even more critical for his chances in November now than they were four years ago. With his solid southern base badly threatened, if not surely eroded -- his hopes for taking Texas, Flordia, Mississippi and Louisiana this year are slim at best -- Carter needs the hlep of Kennedy and his workers in the industrial states which hold the most electoral votes.

No one politician can guarantee the delivery of any particular segment of voters in this increasingly fragmented society, but Kennedy clearly still commands a powerful following.

The belief here is that he will campaign vigorously for his party, will work to defeat Reagan and to elect Democrats. If his efforts help keep Carter in the White House he can claim part of the credit. If the president loses, Kennedy will be blameless. Either way he stands today in a more formidable political position.

His speech here accomplished something else. It domonstrated that he alone among the Democrats has the ability to stir the old party choir, to tap institutional memories, to evoke the history of previous political triumphs and struggles. His actions this week showed that, however fumbling his own campaign had been, he is still capable of seizing a moment and making it his. From his quick withdrawal from the race to his summons to his party from the podium, he was acting with a decisiveness that so often had been lacking in his past.

Whatever happens in the fall, with Carter becoming instantly upon reelection a lame-duck president or Reagan inheriting the problems of that office, Kennedy obviously will play a major political role from his base on Capitol Hill. His assertion of leadership this week also had another effect.

Already many Democrats with presidential aspiration are looking beyond this campaign. Not long ago it appeared certain that this chapter of the Kennedy story had ended after a generation.

Now they find themselves still facing a Kennedy in their future.