It was an elegant fund-raiser-early evening at small and sleek Tiberio Ristorante.

Violinists strolled past tables.The assembled crowed was dressed formally, but relaxed. Some of the best known Democrats of the Senate drifted by-Ted Kennedy (Mass.), Majority Leader Robert Byrd (W. Va), John Glenn (Ohio), Howard Metzenbaum (Ohio).

At $250 a person, it was all for Sen. George McGovern, as he gears up his campaign for re-election.

McGovern is among several liberal senators whose seats have been targeted for particular campaign attention by conservation Republicans, a challenge that has rallied the liberal warhorses and others as well.

This night, the grim issue at hand hit one businessman, seated near Sen. Howard Metzenbaum. "They tell me he's in jeopardy, Howard," the man said over pasta appetizers. "Is George gonna have a hard time getting reelected?"

Metzenbaum answered, "It is a fact that there is a drive on by the new right (to win his seat). We need to have corporate PACs (political action committees)."

"But everyone in my corporate suite is a Republican," explained the businessman.

"The last election," said Metzenbaum, "it was not just Republicans who won, but the far right. They made a dent. They tasted the fruits of victory and they're gearing up to make a far greater dent.I had a breakfast meeting at 8 this morning. We were talking about the money we need to raise."

"Well," said the businessman, "that's why we're here."

Sen. Frank Church (D-Idaho), and Sen. John Culver (D-Iowa), are also among the liberal Democrats whose seats are under seige.

Both have had fund-raisers this week-Culver at Ethel Kennedy's Hickory Hill house in McLean last Wednesday, and Church last Thursday. Last night's was hosted by Sen. Kennedy (who came with Ethel Kennedy), Yankel Ginzburg, an artist and good friend of McGovern, and Giulio Santillo, the owner of Tiberio, and his wife.

Both Kennedys left before dinner began, but not before the senator gave a rather impassioned speech about McGovern, saying that the South Dakota senator had made "extraordinary contributions to the Senate and the country."

Kennedy credited McGovern with being instrumental in bringing the war in Southeast Asia to an end, and called him "a special friend to my older brothers."

"George faces a tough and difficult campaign," said Kennedy. "It's not just a campaign for one seat, but a campaign being fought for the conscience of this country."

It's a tough race in general, Byrd said before dinner. "We're not particularly favored by the numbers," he said. "There are 24 Democratic seats up and 10 Republican seats. That's very unusual. Naturally those kinds of odds mean we'll have to work hard-harder than usual perhaps. So I am rather concerned."

Despite the tough talk, this was an upbeat affair, with Yankel Ginzburg directing table traffic, seating charts in hand.

The senators who stayed for dinner were seated at different tables. "This is the people's dinner," one person said with a grin. "These are Democrats. You spread 'em around."

After dinner, Byrd was asked to play his fiddle. First he spoke about McGovern, and then launched into a variety of tunes including, "Amazing Grace," which he crooned through just like a country regular. He stopped once to demand silence of the noisy guests.

"I don't play for background noise," he told the audience. "I hope you won't think me discourteous."

He played on and the talk stopped.

"There's not much I can add but my gratitude," said McGovern at the end of the three-hour affair.

Earlier he had said about his race, "I don't see how they can get any tougher. I've learned not to take any race for granted. None of them comes easy in my part of the country.

"Bob," he said, turning to Byrd, who had just finished playing. "I've been in politics 22 years and if there was ever a time I felt anti-climactic it was tonight." CAPTION: Picture, Edward Kennedy, Robert Byrd, Ethel Kennedy, George McGovern; by Fred Sweets