They clustered around the speakers at Thompson's Boat House near the Watergate, 200 area Democrats sipping champagne and listening intently as their party's national leaders heaped lavish praise on Ira M. Lechner, a Northern Virginia congressional candidate.

Rep. Lindy Boggs of Louisiana urged them to help "send this good and wonderful man . . . across the river to us in Congress." Rep. Claude Pepper of Florida, champion of the elderly, offered to "visit all those retirees individually and collectively" who live in Lechner's 10th Congressional District. Rep. Morris K. Udall of Arizona said he had a simple message on behalf of his old friend: "Give the poor bastard some money."

For many who had paid as much as $250 to attend the recent fund-raiser, the undisputed highlight was a brief appearance by one of the most famous residents in Lechner's district, Sen. Edward M. Kennedy of McLean. As party workers nudged each other and snapped pictures of the Massachusetts senator, he climbed onto a makeshift podium plastered with bumper stickers.

"I'm here as a friend and supporter and I want Ira Lechner to be representing Ethel and all the children," he said, referring to his sister-in-law and her children who also live in the district.

While some Virginia politicians would argue that having prominent liberal supporters like Kennedy and Udall is of little value in a state as conservative as Virginia, Lechner thinks otherwise.

The 47-year-old former state legislator from Arlington sees his national connections as a valuable asset in his uphill fight to unseat the better-financed Republican Rep. Frank Wolf in November. "Ted Kennedy stopped in to pay his respects, just as Lindy Boggs, Claude Pepper and Mo Udall did," Lechner said. "What it showed was we had a broad base of support in Congress."

Some Lechner supporters, however, aren't as certain Kennedy's support will prove a blessing. "There was a lot of concern that being associated with Ted Kennedy might be a liability," said one key aide who requested anonymity. "We're in a tricky situation because many very liberal people have been Ira's supporters for the past 20 years."

While some downstate Virginia conservatives would have a field day with a Kennedy appearance, Wolf's campaign manager says he does not expect Lechner's nationally known backers will become an issue this fall. "We're going to be talking about what Frank has done as a congressman," said campaign manager Tom Moor. "We don't have any plans to attack Mr. Lechner on the basis of who supports him or doesn't."

Moor says he expects Wolf will use some of the Reagan administration's celebrities, in part to help him raise about $450,000 for the race. Two days before Lechner's Washingtonn fund-raiser, for example, Wolf held a cocktail party at Arlington's Washington Golf and Country Club that attracted more than 200 supporters. They paid $250 each to eat ham and turkey sandwiches with Treasury Secretary Donald Regan, helping Wolf raise an estimated $70,000.

Moor said the Wolf campaign plans to sponsor a number of less costly fund-raising events and at least one other big ticket event at which Transportation Secretary Drew Lewis may be the honored guest. Last spring Presidential Counselor Edwin Meese was feted at a Wolf fund-raiser hosted by J. William Middendorf of McLean, the administration's ambassador to the Organization of American States.

The Wolf campaign has no counterpart to "The Washington Area Friends of Ira Lechner," a list that includes W. Averell and Pamela Harriman, House Speaker Thomas P. O'Neill and former vice president Walter F. Mondale. Lechner aides say Gov. Charles S. Robb, another resident of the 10th Congressional district, North Carolina Gov. Jim Hunt, and Mondale all have promised to campaign for him.

"This kind of thing really helps Ira because a lot of people have known him as the defeated candidate for lieutenant governor--twice . . . , " said Arlington Sheriff James Gondles. "This shows party workers that Ira is a Democrat with credentials good enough to bring a Kennedy to a fund-raiser. It causes them to stop and think, 'Hey, he can win the race and I better get on the bandwagon before the freight train runs over me.' "

"Ira's been around a long time; he's been active in a lot of campaigns and he knows a lot of people and I've done a lot of work for the DNC Democratic National Committee ," said campaign aide Jim Golden. A former deputy secretary of state in Pennsylvania, Golden arranged the boathouse party and subsequent dinner at the Georgetown home of national Democratic Party Chairman Charles T. Mannatt that is expected to raise $25,000.

A Washington labor lawyer with extensive union contacts, Lechner has said he hopes to raise nearly as much money as Wolf, which he acknowledges is his most formidable task. Reports filed with the Federal Election Commission showed Wolf has raised about $179,000 compared with Lechner's $105,000. The third candidate in the race, Libertarian Scott Bowden, has not filed a report because he has yet to raise $5,000.

"Of course we have to stretch a buck," said Lechner, vice chairman of Virginia's Democratic Party. "I think our fund-raising efforts have been really successful and remarkable for a Democrat from a district who is traditionally outspent 2 to 1," he said. "Obviously we're not going to be blown out of the water."

Lechner's strategy differs markedly from that of Herbert E. Harris II, his neighbor from Virginia's 8th Congressional District who is seeking to recapture the seat he lost to Rep. Stanford E. Parris in 1980. "We've had the governor up and we'll have the state attorney general here, but we're sticking closer to home," said Harris aide Peter Intermaggio. "We haven't found that we need to use national figures to get people to come to events."

Pepper says he has few doubts that the Lechner celebrities will have an impact on the race. "These are discerning, wise people who live in the shadow of the nation's capital," he said, standing on the deck of Thompson's Boat House and gesturing toward Virginia. "Is Frank Wolf in trouble? Well, I don't know. But I think this man Lechner will go far. After all, people like Mo Udall and Lindy Boggs are active for him."