Let loose at last from the convention, those motley characters who gave it some life danced and drank themselves far into Friday with impressive vengeance. Carter chieftains Jody Powell, Tim Kraft et al. let loose ties and campaign strains at Xenon until nearly 4 a.m., bumping to continuous disco under green and white balloons. Jimmy Carter had a small party at the Sheraton Center for his big money men and CBS feted Walter Cronkite until well past 3. Uptown at Elaine's Restaurant, governors Jerry Brown and Hugh Carey and a tired chunk of the Eastern establishment media had red wine and linguini with zucchini until almost dawn.

"It was a rip, honey," said Elaine, owner of the famous Manhattan gathering place, who closed her doors at 6 a.m. That's the Way It Was

"I think I'm going to cry," said NBC vice chairman Dick Salante, who had been president of CBS News for a number of years. But he didn't. And neither, as far as anybody could tell, did heir apparent Dan Rather.

"As I began to work through this last convention," Walter Cronkite was saying, at the party in his honor at Tavern on the Green, "I began to think there's no particular reason why Dan Rather has to do the nightly news . . ." Loud, loud laughter.

Every four years CBS, like the other networks, throw an after-convention bash that may be one of the more lavishing office parties around. "They probably spend 50 or 60,000," guessed one CBS employe, "or one minute of air time on a slow day."

The 1980 office party Thursday night was in honor of Cronkite's last convention. There were speeches, there were pictures of him on the walls as a relatively young pup with John F. Kennedy, there were in-house jokes. And there was emotion.

"I guess it'll still go on without Walter," said Andy Rooney of "60 Minutes," "but he has been very important to CBS News -- more important than anything he does. He's an important symbol.

"And you know," Rooney continued, "He's a good guy. He's more interesting than most people. Yeah, he is.I've spent a lot of time with him alone. He thinks of interesting stories and he's very turned on to the minor events in his life or anybody else's life."

And from Cronkite: "I am overwhelmed, I really am . . . even though I know that free drink and booze is a hell of a lure."

That it was. Hundreds and hundreds of technicians, camera people, reporters, gofers, and one CBS president, Bill Leonard (of CBS News), took over the entire Central Park restaurant. The chandeliers glistened inside, the night hung soft outside and everybody ate and drank too much. It seemed that there were half-cows of beef on the tables, endless chocolate cake and infinite Scotch and gin. Back in the food area, the emotion was considerably less and besides, everybody figured that this just may have been Goodbye Party No. 5 for Cronkite in a year that is far from seeing the end of him.

"I've been to three goodbye Walter parties already," somebody said. "There was the affiliates' party, the party in Washington . . ."

"Well, you know how it is," another person said. "Some people have funerals in different cities." Dancing Their Hearts Out

Nothing really got going at the Carter/Mondale victory celebration at Xenon's until after 2 a.m. That's when the tables were folded up after the Roberta Flack and Loretta Lynn show, leaving the dance floor naked and ripe. And so they danced. Oh, did they dance. Conversations and perhaps intelligent thought ceased; the green and white balloons, green and white feathers floated from the ceiling onto the wooden floor. If you weren't careful, you could slip on a green and white Carter/Mondale streamer and break your neck. But then, it was all for the cause.

Jody Powell danced with his wife, delegate hunter Tom Donilon ripped off his tie and danced ferociously with a blond woman, Carter media adviser Gerald Rafshoon did a slow, languid number and Dorothy Henry, Hamilton Jordan's date, took off her shoes.

So did a certain White House staffer who held hers in her hand as she expressed herself on the dance floor.

"Doesn't look like this back home," observed one White House staffer from the Midwest. "Half of these people are so excited to be here."

In a sense, that was true, since White House staffers tend to be workaholics who eat take-out a lot and live unglamorous -- by New York standards -- lives in Washington. But last night, their boss had just been renominated and New York was theirs.

The scene at Xenon: Donna Summer singing "Do It to Me Right," flashing lights, Roberta Flack, Loretta Lynn, and Jimmy Carter's lieutenants right there in the front row. And from their point of view, the president's speech to the convention earlier in the evening was teriffic.

"I thought it was a good speech," said press secretary Jody Powell. "I thought it was a great speech until I came back and heard the network commentators p---ing all over it. Simple-minded bastards."

Along the same lines, the Carter people collected at the disco didn't think Ted Kennedy was disappointing at all. "The media nitpicks everything," said Hamilton Jordon, who had a beer in the first row of tables. "He endorsed the president yesterday, he appeared on the podium tonight. We couldn't have asked for anything better."

But others thought differently. "He wasn't as outgoing as he usually is," said Kentucky Gov. John Y. Brown of Kennedy's podium appearance. "I'm sure that's a strange scene for him to be in. He looked a little uncomfortable."

Added Brown's wife, Phyllis George: "I guess it's hard for me for one night to turn it off."

The Carter/Mondale victory celebration at Xenon wasn't scheduled to begin until 1 a.m., but a crowd had collected early outside the 43rd Street disco, and in a style reminiscent of Studio 54, beautifully dressed bouncers behind velvet ropes kept the undesirables from the desirables. Cameras popped, police were crawling everywhere and the rumors raced -- the president was going to show up, no he wasn't, well, maybe he was. But by 1:30 a good three dozen police were standing in front of the barricades with nothing to do. t

Inside the dark, cavernous place with black columns, a black rug and a giant wooden dance floor, the mood was like a victory dance after the football game. This team had won, and its players turned out to dance: Nathal Landlow, Smith and Vicki Bagley, who've been everywhere this week, Atlanta Mayor Maynard Jackson, and Tom T. Hall, the singer, Carter supporter and close friend of brother Billy.

Everyone wore the kind of clothes you can see walking down K Street at lunchtime: dark business suites and conservative dresses that were only slightly wrinkled by the heat. It was easy to spot the New York disco crowd with their black leather pants, mini lame dresses and David Bowie haircuts.

And then there was author Fran Lebowitz, who came preppy style in faded straight-leg jeans and a navy blue blazer. "I'm a thrill-seeker," she said. "I wanted to look at the clothes."

But is she a Carter supporter?

Nah, she replied, "I'm a Republican. Really." Media War Stories

Elaine's is still Elaine's, but this week, it was Elaine's! Almost any night after the convention, the longtime Second Avenue writer's hangout was transformed to a mini-Washington where reporters and the reported could dine over blue-checked tablecloths or under Paris Review posters. Regulars David Halberstam and Gay Talese had plenty of company.

"Definitely a place to see and be seen," said Transportation Secretary Neil Goldschmidt, just one of the non-literary fish out of the water Elaine Kaufman had in this week. Some others: national security adviser Zbigniew Brzezinski, Jeff Carter and Gerald Rafshoon.

Yesterday morning, things, as Elaine said, were ripping.It started out as two small parties, one given by Los Angeles Times reporter Bob Scheer, another thrown by producer Marty Bragman. But pretty soon, maybe 200 people had crowded into the dark, narrow restaurant playing Willie Nelson on the juke box and telling 1980 Democratic National Convention war stories. Squashed inside and table-hopping were writers Ken Auletta, Roy Blount Jr., Pete Hamill, Lally Weymouth, editor Clay Felker and assorted reporters and editors from the New York Times, the Washington Post, the Los Angeles Times, the Village Voice and on and on and on.

"It was just a real -- I mean, if you were giving a party at home and prepared it by yourself, that would be atmosphere," said Elaine, who ate it all up.

At 6 a.m., the last soul wandered out onto Second Ave. and 88th. At 6:30 a.m. Elaine locked up. At 7, everybody was in bed. You would think.