He was sitting on the edge of the big blue leather chair - his chair. It's the same chair he has sat in for the past 10 years, behind the large, glass-topped desk with the sign in front that reads, "Walter E. Washington, Mayor, District of Columbia." No one else in his century has held that title.

The mayor folded his hands on top of the desk, rocking slightly in anticipation. He occasionally sipped coffee from a blue and white china cup and sometimes nodded his head up and down in agreement. He was waiting for a reporter to finish reciting the litany of reasons some people - including the mayor's own corporation counsel - have been giving to explain why Washington should not seek reelection this year.

When the reporter finished, the mayor said he found the logic "interesting" but not persuasive enough to stop him from seeking another term.

"I've not ruled it not," he said, "largely because I've been . . . talking to a lot of people. I've gotten pressures from numbers and numbers of people and other people who have looked at all those factors - neither negatively nor positively - and said, 'Please don't rule it out."

"I've maintained an open mind but that only keeps your mind open. It doesn't exactly dictate what you do."

The fact is, the mayor said, that people are suddenly excited about this city and what is happening in it, and they tell him that he is the reason for what's happening. No matter what people say publicly. Washington said, deep down they know he has run the city with a steady hand.

In one way or another, this is what the mayor is telling his audiences these days, whether they be businessmen and potential campaign financiers at a dinner of the Metropolitan Washington Board of Trade; disco dancers at the Foxtrappe; well-wishers at his 10th-year-in-office celebration or fellow fraternity brothers of Omega Psi Phi.

He acts like a candidate on the verge of launching a campaign. He grants interviews to the same reporters whose questions he ducked only months ago. He trumpets his plans for property tax relief and plans for doling out dollars to rebuild rundown neighborhoods. He orders city aides to prepare reports showing how much he has done for the city during his past 10 years in office.

Sometimes during the next three weeks Washington told a WRC-TV interview last night, his political plans will be announced.

He seems amused by the suspense he can create by continuing to leave his intentions up in the air. His loyal followers, likely opponents and the reporters who chase behind looking for a scoop, are all awaiting the big announcement.

But Walter Washington will not be rushed.

"The interest groups in the community who realize who their friends are and will be are ready and all you need is a bugle," said one Washington supporter, Calvin W. Rolark, a weekly newspaper publisher and community activist. "Everyone is waiting for a signal from the mayor.We're in training, you might say, just relaxing and waiting for the big kill."

In th view of most of his opponents and some of his friends, there are several reasons why the mayor should discover life after city hall by bowing out of D.C. government gracefully while he can.

His close friend, adviser and general assistant - Joseph P. Yeldell - is being investigated by a federal grand jury, whose probe is now ending. But even if Yeldell is indicted, the mayor said in the interview, that would not stop him from seeking another term.

"I don't think that's a terminal factor for me," the mayor said. "I just hope it doesn't occur because I think he's working hard. He's putting his talents into effective public service."

Other reasons include the repeated accusations that he has surrounded himself with inept administrators who lack a sense of responsibility to city residents. One department head has acknowledged violating the city's conflict of interest code.

Then, there is the problem of the millions of dollars in federal funds that are in jeopardy because of substandard conditions at some city facilities. The mayor himself has been found in contempt of a court order to speed up processing of welfare applications. Water bills go out late, property tax bills are going up and the city's population is going down.

And there are the personal reasons Next month the mayor will turn 63, and he was spent nearly two-thirds of his life in government, still lives in his wife's family's home on a side street in a once run-down section of the city. And, a reporter points out to the mayor, he does not appear to have become a wealthy man over the years.

"That's right," the mayor said, nodding his head up and down.

"What would you want to do if you weren't mayor?" the reporters asks.

"I haven't thought about it," the mayor responds in a gruff, let's-move-on tone. Then, in what some may consider a subliminal slip, he adds, "I have from now till January (the time that his present term ends) to think about it."

Some people close to the mayor have already thought about it. One is Corporation Counsel John R. Risher Jr., who said he does not plan to stay in office beyond January and thinks the mayor should follow the same route.

"I think he's been in office enough and he's suffered enough, if not more than he'd have a right to expect," Risher said in a recent interview.

"Next October, he will have completed 11 years of service. I think he's done enough. He ought to get out and make himself some money," said a longtime friend of Washington who asked not to be named.

"Another reason I don't want him to run," the friend adds, "is because I don't have any confidence in him to win, and I don't want to see him defeated."

It is difficult to assess the mayor's political strength because, among other things, his popularity seems to rise and fall, just as his own public profile fluctuates from high to low key.

There are times when he seems to be virtually invisible at city hall and in the community and his aides explain that he's home "working the phone." And then there are the times when he's all over the city, dedicating projects, attending social functions at a fast clip.

But there are some constant feelings that are expressed about his administration by those who think he should call it quits. One of those is that he has failed to make the transition from the follow-the-orders bureaucrat he was during his years as appointed mayor (1967-1974) to the take-the-lead chief executive style that many expect of an elected mayor.

"If you called the city's 100 leading businessmen and asked them what was the mayor's greatest achievement, 80 percent of them would say he kept the lid on during the 1968 riots," a leading city banker said privately. "That was appropriate then, but just keeping the lid on is not a progressive stance."

Most of the political polls taken over the past nine months have shown that the mayor trails City Council Chairman Sterling Tucker and council member Marion Barry as a preferred choice for mayor. A Washington Post poll of 932 Democrats voting in the Nov. 8 school board election found that two of every three persons surveyed who said they voted for Washington in 1974 would not vote for him again.

But the mayor doesn't make much of these polls. "I've seen them come and go and I don't think that this far out (from the election) the polls are significant," he said.

Unlike Chicago and other places where there are "tight and unyielding political organizations," the mayor said, the situation is "more fluid" in Washington because "hard ball politics" is relatively new and this is "a very difficult city to organize."

There are many diverse groups who claim a share of political power in this town, he said, adding, "I don't think anybody has staked out any turf that I've been sufficiently to say they've got it."

The mayor's political musings could be taken as wishful thinking, if it weren't for the fact that many people agree with what he's saying, and some profess no strong attraction for the two other major candidates - City Council Chairman Sterling Tucker and council member Marion Barry.

"Under normal circumstances, I'd say he's been there for 10 years, he's 62 and someone else ought to get a crack," said a senior member of the politically influential Board of Trade. "But I'm not sure whether Sterling or Marion are the guys to be able to do it."

One puzzling aspect of the mayor's political strength is the fact that some elements of his style and image are viewed in totally opposite ways. Among all but the mayor's staunchest supporters, these perceptions seem to change sharply depending on how they feel about the city.

What is sometimes regarded as procrastination by the mayor later appears to be caution. A hat-in-hand approach to Congress and the White House can turn into the proper dose of pragmatism. At one point, the mayor is too old, too conservative and too easy-going to do a good job. At another point, he is viewed as just the right kind of person to be mayor of the nation's capital.

"Do you think that Queen Elizabeth would come here to visit Marion Barry?" one mayoral aide asked.

Washington's supporters also believe he exudes more personal warmth than Barry or Tucker. "You have a sense of who Walter Washington is," said the Rev. A. Knighton Stanley, pastor of Peoples Congregational Church. "For many folks, he's the boy next door who made good. There's a fatherly image about him that people like and appreciate. He impresses people in a very homespun kind of manner."

The mayor also has the political advantage of being an incumbent, the only mayor this city has known in more than a century. And he is black in a 70 percent black city where power has always been associated with whites.

That, Stanley asserted, is one reason why the criticisms of inefficiency in the mayor's administration by the major news media in town are regarded skeptically by Washington's supporters.

"The image of a black man is still such that he does not have to prove inefficiency. That's already assumed when he walks into the room," Stanley said. "He's got to spend the rest of his time trying to prove he's not inefficient."

Walter Washington is not reluctant to act like a candidate these days, blowing his own horn just to let everyone know he's still there and telling potential campaign donors to "hang loose" before throwing their support to already announced candidates."

He delights in watching Barry and Tucker jab at each other, feeling, according to some aides, that the longer those two fight, the better it is for his own candidacy. And he jokes about the aspirations of those who want to take his job.

"This is substantive kind of work that the mayor of the nation's capital has to deal with," he said. "I sometimes wish they's spend a week here in training."

On his own part, the mayor's pre-campaign efforts are well orchestrated. Most of his community meetings are staged by a group of longtime supporters, who at times have bused senior citizens in to attend the events. Former campaign workers pose as "citizens" and ask prepared questions on television call-in shows. And so prepackaged are some of the events that one skeptic in the mayor's entourage once told a reporter, "I don't get the point. The same people show up at all of these things."

The mayor appears to love it. "I feel so good I may go for 10 more years," he told a cheering gathering of his followers late last year at a downtown hotel rally.

"I see the unions and I see some good business stuff here. I see ward leaders and I see my wife next to me. What else does a man need before he announces?" he asked.

The audience was cheering, anxious and applauding with expectation.But Bennetta Washington cautioned: her husband: "Don't get carried away, dear. Don't get carried away."