It was a hot an sticky summertime night at the Capital Yacht Club. The shimmering reflections of shore lights danced on the ripples of the Potomac River. Inside the waterfront club, the beef burgundy and sea trout were gone and the maitre'd had ordered the champagne glasses filled.

Mayor Walter E. Washington, his wife, Bennetta, and his campaign manager sat at the center table. Raymon Bady, wearing a white suit and gliding across the floor, microphone in hand, was sounding very much like Arthur Prysock as he crooned in a velvety baritone:

"Who can I turn to? . . . My heart wants to know and so I must go where desting leads me . . ."

Bady, a city employe who has known the mayor for 15 years, dedicated the song to Washington, and perhaps appropriately so.

For as the mayor plunges into the final weeks of campaigning, he is turning to old friends, longtime political allies, city workers and a few new faces here and there in an effort to eke out victory in the Sept. 12 Democratic primary.

No one in the campaign organization talks about winning a solid majority of the votes as a mandate for the 63-year-old mayor, who has been in office more than a decade. The mayor can win this 3-way race, campaign planners say, with 45,000 votes - 6,000 less than he received in a 2-way race with Clifford Alexander in 1974.

While others criticize the mayor's performance in office, he boasts about it as the major reason he should be reelected. He seems comfortable with the consoling logic of an associate who explained recently. "The mayor has been attacked on his record. But at least he has a record."

"Nobody's come forward with anything other than what I'm doing and I'm already doing it better," Washington told a gathering of upper-income blacks last week at the red-carpeted Blair Club in Silver Spring.

When you get rid of the program areas, what you get down to is a personal commitment to the city, integrity and trust. That's what you're going to get down to. When you look at that with the other candidates, what else can you do (but vote for me)."

Seldom does he paint a clear portrait of his vision of the city's future.Hardly a single new program has been unveiled. Instead, the mayor counts down the days until the election.

Two months ago, after the mayor officially announced his long-anticipated intention to seek reelection, his campaign organization was fragmented.

While his two major opponents - City Council Chairman Sterling Tucker and Council member Marion Barry - took their campaigns to the wards at wine sips and cocktail parties, the mayor got most of his political milage out of high profile official appearances. His campaign office was barely staffed. He used posters and literatures recycled from the 1974 campaign. Much of his time was spent in his District Building office.

A poll taken by The Washington Post in June showed Tucker the choice of 24 percent of the 1,020 registered Democrats polled, with 20 percent for Washington and 18 percent for barry. The largest group of voters, 35 percents, was undecided.

Worse yet for the mayor, however, the poll found that two of every three persons interviewed who said they had voted for Washington in 1974 would not do so again. Thirty-one percent of all those interviewed said that under no circumstances would they vote for Washington Sept. 12.

"I think there has been a softening and some slippage," Warren Graves, coordinator of field operations for the campaign, acknowledged last week. "But there have been no defections."

The belief that one-time Walter Washington supporters have not switched sides irreversible is the linchpin of the political theory that his strategists hope will make the mayor victorious Sept. 12.

"The number one priority," said one mayoral confidant, "is to get back the people who were Walter Washington supporters in 1974 and have drifted, and you get whatever else you can . . . When you have limited time, limited resources and limited staff, you go after the people who are most likely to be persuaded."

Washington's campaign workers are combing through returns from past elections to identify the precincts that supported the mayor strongest in 1974. They are also looking at the returns from Tucker's 1974 council chairman race and Barry's campaigns for council at-large in 1974 and 1976. By combining the findings of these searches with records on which precincts have the highest voter turnout, the campaign has developed a list of nearly 70 top priority precincts in various parts of the city.

The Washington strategy is admittedly modest, campaign officials said, and scaled down by the fact that with three major candidates in the race, winning a majority of the votes is unnecessary. A simple plurality will do.

"In my way of thinking," Washington campaign field operations director Graves said, "If anybody gets 45,000 votes in this election, he can win it." Graves expects about 120,000 Democrats to vote.

Unlike the Barry and Tucker organizations, which began door-to-door voter identification canvassing months ago, the Washington organization is doing that chore by telephone now. They plan personal visits only after Washington supporters have been identified, campaign workers said.

Some strategists for the mayor are counting on him as the incumbent having an edge with the most crucial group in the election - the undecided voters. "The undecideds are turned off by these three guys who've been around a long time," one mayoral confidant said. "But theres' a tendency when you're undecided to play it safe. You end up saying, 'Sure, there's been an administrative mess, but at least I'm getting fire and police service."

"What the campaign strategy is," Washington told one audience last week, "is to go where people are willing to have you come because they understand."

His is often a brisk campaign of many brief appearances as he tries to pack into the final closing days the same activities that his opponents have spread out over months. At times, he has three and four fundraisers in one day. He juggles schedules and, depending on the audience, sometimes doesn't decide to come until 20 minutes beforehand.

Washington has lost 23 pounds by his own count in the last month. His shirt collars sag around the neck, and he pulls out the waist of his pants with a smile to show a reporter that some of the paunch is gone, too.

Mrs. Washington is always with him, backing away to the side when he hits the dance floors of the disco's occasionally being his one-person "Amen corner," but always there.

In a contest in which no key issue divides the three principal candidates, Washington has adopted the posture of a pragmatically mdoerate, timetested statesman. He portrays his two opponents as ambitious and wild-eyed political dreamers who would promise the world to get where he's already been.

When it comes time to talk about housing, for example, he lists specific projects built during his administration by name, location and number of units. "They don't even know the names," he said at one recent candidates forum, as Tucker and Barry sat silently by.

Much of the preacher like oratory is gone from Washington's campaign rhetoric these days. He saves that mostly for church. In its place, there is a more reserved, softer and slower-speaking mayor who some campaign intimates believe better fits the image of a respectable and fatherlike chief executive.

"Change goes two ways, up and down," he told one audience at the Georgetowne Inn. "You can change for the better or you can change for the worse. This is no time to start talking change that involves on-the-job training for mayors. We do not have the time . . . I've already mastered the system."

Erlena Bland, a school librarian and the wife of a physician who lives in the black, upper-income Kalmia Road area of northwest Washington, was one of those at the Blair Club reception.

"With Walter," Bland said, "I know what he can do. I know what he can't do. I know when his hands are tied. That's good enough."

Solidfying Walter Washington's constituency means bringing together many older city residents who are black, moderate in their views, churchgoers and homeowners. This includes many of the people in the "Gold Coast" neighborhood of upper northwest Washington, where much of the older black middle class lives.

THe mayor is also making concerted efforts to win over voters in Wards 5 and 7 in northeast and southeast Washington. Even though he lost Ward 8 (Anacostia) to Alexander in 1974, he expects to win it this time and his campaign is placing some organizational emphasis there.

Washington's campaign planners are also hoping to gain some support from very young voters and have scheduled several appearances by their candidate in city discos.

But, the major new voter outreach effort on Washington's behalf is a virtual second campaign being run by the political arm of the Greater Washington Center Labor Council, the umbrella group for organized labor in the Washington area.

Minor Christian, first vice president of the Hotel and Restaurant Workers Union Local 25, is coordinating the labor effort, which he said involves 11 full-time persons and which he estimated would cost $30,000.

Washington campaign planners are also expecting a political boost from the Taxicab Industry Group, headed by William J. Wright of Capitol Cab Association. TIG already has Washington bumper stickers on many city taxicabs and plans to use cab drivers to ferry voters to the polls on Sept. 12.

The campaign is also expecting strong support from many of the city's black clergymen, who have traditionally supported Washington, as well as from senior citizens, another Washington stronghold.

All along, the Washington campaign strategy has been based on the premise that the longer lasting efforts of Tucker and Barry would begin of peak in the hot and humid political dog days of August while Washington would just be gaining momentum.

The other side of that proposition, however, is the challenge to the mayor's organization to solidify in less than half the time it has taken the others. Campaign planners claim that they can do it.

"The mayor's rock-ribbed constituency was much larger than anything they (Tucker and Barry) started with" Graves said. "When you say we started later, it doesn't mean we started at zero."