For Jimmy Carter and Edward M. Kennedy, the 1980 rivarly had come down to one last tango in New York -- a floor fight over the economic planks of the Democratic platform.

There was Carter, wanting most of all to have Kennedy beside him Thursday night in a dramatic display of party unity. And there was Kennedy, wanting nothing short of absolute victory on those key economic issues as a prelude to any possible display of political affection.

With Kennedy having abandoned his candidacy, today was to have been the day for negotiations and reconciliation on the platform disputes. But the two camps held no negotiation sessions during the day. The Kennedy forces said they could not compromise, and the Carter forces said they could not give in.

But then tonight came Kennedy's powerful speech, which stopped the convention with emotion. As the convention hall erupted in cheering, even Carter delegates were clapping.

Fussing over the platform is the sort of thing that traditionally produces political convention boredom. But in 1980 the issues were Kennedy's liberal employment programs vs. Carter's desire to practice fiscal restraint.

"We will not compromise on the issue of jobs!" Kennedy thundered tonight.

In the Carter situation room trailer the president's advisers recognized the emotion stirred by the speech for what it was -- a moment that could make or break the president's vital need for unity with the liberal wing of the Democratic Party.

So within minutes for a floor fight that began hard and bitter, the Carter forces were turning potential disaster into unity with a single bold gesture: giving in.

Instead of time-consuming roll calls to decide contentious planks, the two sides agreed on voice votes.

Only an hour earlier in the Florida delegation Carter supporters and Kennedy aides had been cursing one another, red-faced with anger, questioning each other's parentage. Now, Charles Whitehead, a Carter man, picked up the green telephone that signaled him with a winking light. When he hung up a moment later, he too was winking -- at his enemy the Kennedy man.

"They're really trying for a vote vote," Whitehead said. "They're trying to put together a package . . ." Throughout the convention hall similar scenes were taking place in other delegations where members had been at each other's throats -- literally.

At stake were economic planks 1, 2, 3, 4. One called for wage and price controls. Two dealt with budget controls. Three advocated a $12 billion program for creation of jobs. And No. 4 opposed high interest rates.

Even without the emotional impact Kennedy's speech had on the convention, the Carter forces recognized they would lose on planks two and three. They thought they could win on No. 1. So a deal was struck that would avoid the divisiveness of roll calls and, as one White House official later explained, "Both sides got out of it what have happened anyway."

Kennedy accepted a loss on wage-price controls, which his aides decided was less central to the jobs issue so crucial to their cause.

But Carter accepted defeat on the other planks.

The initial telephone call to break the impasse was made within minutes of Kennedy's speech by Carter's chief campaign strategist, Hamilton Jordon, to Kennedy's political director, Carl Wagner. The discussion broadened to include several other aides on both sides, with House Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.), the convention chairman, acting as mediator.

The sides agreed that O'Neill would make the calls on the voice votes, sticking to the agreement that Kennedy won on two, three and four and Carter on No. 1.

According to Kennedy aide Paul Kirk , the deal was proposed by Mike Berman, a counsel to Vice President Mondale and convention aide to Democratic National Chairman John C. White.

Kirk said later, "We're delighted with the development of a platform that comes closer to the principles that Sen. Kennedy advanced in this campaign."

In the Florida delegation, after the voice-vote compromise, the name-calling was replaced by friendly smiles.

Tim Hannan, Kennedy's old college roommate and close friend, smiled at a Carter delegate he had earlier profaned. "Well, this heals a lot of wounds," Hannan said. "This makes it better . . . I wouldn't be surprised now to see Ted back here beside Carter on Thursday."