Marion Barry, basking in his apparent narrow victory as the Democratic nominee for mayor of the District of Columbia, leaned back in a swivel chair at his campaign headquarters yesterday and savored for a moment that special feeling that comes only to the victor.

He talked about the conversation he had with Mayor Walter E. Washington in which they discussed "getting together and talking about the transition" before the torch is passed next January.

"He was very cordial," Barry said, smiling, "I told him I thought the figures were going to hold up and I thought we should try and get the party back together. He agreed."

There are still about 5,000 ballots to be counted before the winner of the close Democratic primary is certified. And there is Republican Arthur Fletcher to be faced in the Nov. 7 general election. But yesterday the town seemed to be paying court to Barry.

The telephones rang and rang at the spartan Barry campaign headquarters on the second floor of what once had been a fur store at 12th and G streets NW.

There were hearty congratulations from the board of trade businessmen who had put most of their money on Walter Washington and City Council Chairman Sterling Tucker.

John L. Ray, the long-shot mayoral candidate who dropped out of the race and endorsed Barry, came by to report that ministers who had denied Barry their pulpits in the hot September closing days of the campaign were now "anxious to meet with Marion at a breakfast we plan to hold soon."

Everybody knows who the winner is," Barry laughed.

Later, Barry took a call from one top board of trade official who was told by Barry, "We need a lot of help now, so get ready.You know I'm not bashful, so I'm going to be calling on you."

Only the organized labor officials, who ran a separate campaign for their man Washington, had not called yet, Barry said. "They'll come around eventually, they'll all come around."

Mayor Washington's supporters, Barry said, will be willing to side with him now. "I think I was their second choice."

Barry said he has also talked to Tucker and D.C. Del. Walter Fauntroy, Tucker's mentor during the mayoral campaign, about getting all the members of the Democratic Party to help him in the general election.

"We were split in this election," Barry said about the city's Democratic State Committee. "There'll be some scars because some people were really hurt that Sterling lost."

For Tucker, who still has three more months as an apparent lame-duck council chairman, it was a day to finally face the music of reporters' questions.

The council chairman met with a half-dozen reporters in his office, not as a press conference, Tucker's press aide, Alan Grip, emphasized, but merely to answer the queries of all who had tried unsuccessfully to get in touch with Tucker the day after the election.

Tucker was reserved, speaking in quet but confident tones as he sat at the end of the table, fielding each question with complete but not the usual elaborate answers. He never conceded defeat, but some of the questions assumed that he had. And he answered them anyway.

What would he do when his term as council chairman expires Jan. 2, a reporter asked.

"I don't know yet," Tucker said quietly, adding with a hint of humor and a slight forced smile, "I have a feeling that someone, somewhere, might want me."

What would he like to do?

"I'd like to be mayor," he responded, in a quick, matter-of-fact way.

Tucker said he would ask both Barry and council member Arrington Dixon, the Democratic nominee for council chairman who is unpposed in greater than usual role in shaping next year's city budget. "I hope to pave the way for a smooth transition," Tucker said.

He also said he does not plan to support Republican nominee Arthur A. Fletcher, who said Wednesday he would ask both Democratic losers to support the nominee of the party."

Tucker reserved his strongest words for the editiorial page of The Washington Post, whose Aug. 30 endorsement of Barry, followed by five more editorials championing Barry's candidacy, was seen by many as a key factor in the final days of the campaign.

"At one point I wondered whether The Post had become Marion Barry's campaign manager," Tucker said. But Tucker said he was not bitter. "The Post did what it felt it should do, and said what it felt it should say."

Tucker said he plans to resign as president of the Coalition for Self-Determination, which was credited with pushing through Congress the constitutional amendment that would grant the District of Columbia full voting representation in Congress. He said he thought Del. Walter E. Fauntroy should take his place.

Tucker conceded that Barry's campaign strategy of linking Tucker to Washington "worked to some degree." And he ruled out taking a job in a Barry administration, a question that arose because he and Fauntroy were prepared to ask Barry to accept a job in a Tucker administration in return for dropping out of the race.

Bu Sterling Tucker would not actually concede defeat yesterday. "I owe it to those who suported me to stay in the race until such time as they are satisfied (that all the votes are counted)," he said.