Forget what you've heard. The tuxedo, and not anything else, is the great leveler.

Stuff a bunch of Cabinet members and reporters into black tie, hand them plates of sushi and just try to identify the gadflies. But that doesn't mean people went to Saturday night's annual White House Correspondents' Dinner just to have fun.

"Everyone here is working tonight," said NBC News President Larry Grossman.

"I always come," said Ralph Nader. "You've heard of the fourth estate? Well, the White House Correspondents' Dinner is the fifth estate. It's gracefully efficient. You meet so many people you'd want to have lunch with or see. Where else can you chat with the president of NBC News and the head of RCA?"

Or with any number of jovial administration officials (Attorney General Edwin Meese, Defense Secretary Caspar Weinberger) and tuxedoed and gowned members of the press (ABC's Sam Donaldson, CBS' Lesley Stahl from the television camp) and stray celebrities like American National Theater director Peter Sellars. It was a night of amusing juxtapositions: the great practitioners of schmoozing fine-tuned their technique; President Reagan congratulated reporters who won awards for splashing the controversies of his administration across the front pages and over the airwaves; and touchy subjects were merely alluded to.

Take the delicate way outgoing association president Sara Fritz of the Los Angeles Times asked the press corps, the White House staff and the Secret Service for a "new era of cooperation" at a time when, as she said, "the White House sometimes uses security to keep the press at bay." Or the way she thanked President Reagan, who sat next to her at the head table, for attending the dinner.

"We recognize this has been a very hectic and difficult time for him," she told the crowd of more than 2,000 in the Washington Hilton ballroom, and then invited them to join her in "a hearty and sincere toast."

(Translation of "hectic and difficult": congressional defeat on aid to the Nicaraguan "contras," budget battles and continuing debate over Reagan's upcoming visit to the German military cemetery at Bitburg, where 49 Nazi SS soldiers are buried.)

Many of the people at the party will be leaving with Reagan for Europe tomorrow, whether at his side on Air Force One or several rows back in the press pool.

"Bitburg made the visit from a news standpoint," said Los Angeles Times Washington bureau chief Jack Nelson. "You can try to write a story about the economic summit, but nobody's talking about anything but Bitburg."

Except for the people from the administration like White House counsel Fred Fielding, who begged off with, "I'm just like everyone else here who's not talking about Bitburg."

White House deputy chief of staff Michael Deaver was on the original advance party for the trip and then returned to West Germany to find a concentration camp for Reagan to visit. As he was about to sit down to dinner, he said tersely he thought the trip would be "fine," then added, "I really would like to enjoy this evening without talking about it."

U.S. Information Agency Director Charles Z. Wick, who earlier called Reagan's plans for his trip "a tragedy," and said that "the Russians are going to have a field day," said Saturday, "I don't want to say anything about the trip. I think enough has been said about it."

But as Agriculture Secretary John Block wearily worked his way to the lobby sometime after midnight, he said, "I think the worst is over. I think it's going to begin to run in his favor. I think the people -- after they've heard enough about one thing -- they'll say, 'He's the president. He's entitled to his own opinion. He thinks we should reconcile with the Germans,' and they'll be behind him. They like him. They voted for him."

The dinner was preceded and followed by lots of receptions, and the corridors were packed with people squinting at tiny signs outside the small rooms rented for the occasion, trying to figure out whose drinks they were about to imbibe.

With all those reporters around, news sources had two options: profess ignorance about the issues of the day or craft a graceful version of "no comment."

"I still get a lot of calls," said Pete Teeley, George Bush's former press secretary, selecting the former method. "But when they call me I say, 'If I tell you anything, it'll be more than I know.' "

And choosing the second was political consultant and former White House deputy political director Lee Atwater: "We have nothing to say," he said, standing next to Margaret Tutwiler, the Treasury Department's assistant secretary for public affairs and public liaison. Then he added, laughing, "We have nothing to fear but truth itself,"

Comedian Mort Sahl, the darling of liberals in the late '50s and early '60s, entertained the assembled during dinner with jokes about latter-day liberals. The audience and Reagan, judging from the general and specific guffaws, found it all quite pleasing.

"The liberals are always coming to me thinking I'm a liberal to work for candidates," Sahl said. "Norman Lear, who is the prince of liberals in Southern California, Norman Lear came to me about Jesse Jackson three years ago and we had the following encounter, which is verbatim.

"He said, 'Mort, will you help me with Reverend Jackson's campaign?' That's what he called him: Reverend. The same people called Ellsberg 'Doctor.' I was a sergeant in the Air Force; if you want to address me as that I'd appreciate it -- even though David Stockman took my pension away. So Norman said, 'Will you work for the Reverend Jackson?' I said, 'Gee, I've been out of town -- who is that, is that the black man?' He said, 'To tell you the truth, Mort, I haven't ever noticed.'

"That's the ultimate liberal."

Yesterday, Sahl said he left out a few jokes he had planned to include.

"I was going to use 'You can go to Bitburg but most of them are in Paraguay.' That was one," he said from Los Angeles, where he had returned yesterday morning. "Also, 'I spent the day going around Washington visiting the monuments to the Founding Contras.' Those are the things I didn't get to because we were limited on time."

When Sahl finished on Saturday night, Nancy Reagan gave him a kiss.

Reagan provided a few jokes of his own, touching on the press, the Cabinet and his staff, but avoiding other issues in the news.

"It's my job to solve all the country's problems," he said in his remarks, "and it's your job to make sure no one finds out about it."

Referring to Deaver, newly ascendant communications director Pat Buchanan and those times when photographers and reporters gather around for "photo opportunities," Reagan said, "Photo ops are changing. The old Deaver rule was 'No questions.' The new Buchanan rule is 'No answers.' "

Then he pledged his allegiance to the concept of a free press.

"We're all Americans together and we believe in the same ideals," he said, and he ended with, "It's good to be here and for you folks on the beat tomorrow, sleep late. I'm going to."

As he and Nancy Reagan left the ballroom, the standing ovation followed his path like a receding wave.