"Ladies and gentlemen," the familiar Kennedy voice echoed throughout the Shoreham ballroom last night, "WILL THE NEXT PRESIDENT OF THE UNITED STATES COME TO THE HEAD TABLE!!!"

And out they marched. Almost all of them. The band played, appropriately, "I Left My Heart in San Francisco"--in honor of the site of next year's Democratic convention.

Mondale! Glenn! Hart! Askew! Hollings!

They were there to roast Rep. Morris K. Udall for his birthday, and the rush to be funny was on. A member of their club in 1976, Udall recently decided against playing the '84 sweepstakes.

The other Democratic noncandidate, Sen. Edward M. Kennedy of Massachusetts, was the master of ceremonies and if the convention were today, and humor was the major deciding point, Kennedy had it by a long shot.

Some Kennedyisms:

* "The last time there was this much presidential ambition in one room was the last time my staff sat down to lunch."

* "Now I know that the campaign has started early, but it seems to me that the pace is much slower than it was in 1980. After three months in my campaign, we had lost more states than you fellows have ever even been in."

* "Of course, tonight, Alan Cranston is in Alabama for the upcoming straw vote . Actually, I've been encouraging his campaign. I told him, 'Keep up that idea of a 68-year-old presidential candidate. I may need it myself someday.' " (This brought down the house.)

* "As you know, there's another great political activist who's not here tonight: Henry Kissinger. By the way, Henry is secretly working for all six candidates."

It was more like a five-hour dress rehearsal for 1984 than a political roast--a virtual cattle show of Democratic candidates making a rare unified hometown stop. Posturing and preening was the order of the evening.

Since first is where every candidate likes to be in any kind of vocal contest, Kennedy staved off any potential jockeying by picking names out of a hat. Askew won. Each roaster was asked to limit remarks to three to five minutes. And, of course, to be funny. Some of them actually were.

Ernest F. (Fritz) Hollings got a standing ovation, even from his rivals on the dias. "I'm dying to get into this race," he said. "Maybe the best way to do it is the way ol' Mo Udall did--get out! Fritz Mondale got out in 1976 and they made him vice president.

"I thought that maybe I should take the Jimmy Carter approach. So I took out an ad in Playboy. I'm lusting for the nomination."

Everyone roared. He soldiered on.

"Everyone thinks Cranston is riding the crest of the nuclear freeze. In Alabama, he's going to win the straw poll. But let me tell you something, down there they think the nuclear freeze is a dessert."

Even singer John Denver, one of Udall's longtime environmental pals, got into the act. He sang a song he wrote. It was called "Ballad of Morris Udall." It went like this: "I'll sing you a song of Morris Udall and all the things he's done." That was the end of the song.

The evening opened with a jungle of a cocktail reception. About 1,200 Democratic junkies and reporters crammed a steamy room before dinner. The familiar election-time contingent of national political reporters lurched in the wings, undoubtedly scribbling notes for a later date.

Network cameras hovered and all the candidates accommodated.

Well, almost all.

"No questions," snapped an overprotective Mondale aide, pushing reporters out of the way.

"Now, I've asked you politely," the aide warned when a reporter for Women's Wear Daily persisted.

Mondale, who bombed on the podium, worked the crowd like it was his local supermarket, shaking hands briskly and moving on.

"We promised we wouldn't let anyone ask him questions," said another aide glued to Mondale's back. "He didn't want to upstage anyone tonight. You know how unfortunate that would be."

Meanwhile, John Glenn stepped over the velvet ropes into the press pen to say hello. He was a portrait of patience.

Rubin Askew held forth under the blinding lights. He was explaining to a line up of reporters why he thought he could still win. He's trailing in the polls.

"Polls are irrelevant," he quipped. "Ask Jane Byrne."

Later, on the podium, Udall joked of Askew's campaign: "Rubin Askew continues to campaign in obscurity, apparently waiting for the right moment or maybe the right year. He has made political subtlety an art form. I've heard of invisible primaries, but not invisible campaigns."

Inside the ballroom, everyone got birthday hats and chocolate cupcakes with little white candles. Actor Cliff Robertson introduced the seven-minute film on Udall's career, and then Mo and Ella Udall swooped in under a halo of lights and exploding flashes. Hundreds of red, white and blue birthday balloons shouted "Happy Birthday, Mo."

The $100,000 raised from the dinner will go to Independent Action, Udall's political action committee. Tickets sold for $150 each.

"The irony of this whole thing is that not running for president seems to be more lucrative than running for president," said Ed Coyle, executive director of Independent Action and a Udall adviser.

Udall, a former basketball star known for his dry wit, took himself out of the presidential running in February, saying he would be "a day late and maybe several dollars short."

Though the Arizona Democrat acknowledged at the time that he has been troubled by Parkinson's disease, an affliction that ultimately causes muscle deterioration, he said the illness played no part in his decision.

"I think he's finally come around to accepting his role as senior statesman," said Ella Udall, who goes by the nickname Tiger. "I think he'll be a factor to be dealt with next year."

In the end, everyone sang Happy Birthday and the candidates enthusiastically posed behind a rather large chocolate cake. For about five minutes. You would have never guessed they were rivals.

"Let's be gentle with each other in these next few months," Udall advised the candidates. "Let's avoid what we usually do--form a firing squad. Since we usually arrange it in a circle."