This is a new Marion Barry, Mayor Marion Barry. He strides briskly through the door of the Madison Hotel 20 minutes late. Never mind. Never mind that he had said the coffee shop. "What's open around here," he asks, heading straight for the Montpelier Restaurant, where the oil sheiks, the princes and the diplomats dine. Bursting through the doorway, he walks without escort to a table near the rear and asks the waiter for a glass of rose wine.

No more lunch-time chats in basement restaurants on 13th Street trying to convince reporters that he really will run for mayor. No more having his secretary try for last-minute reservations at Sans Souci and having to respond to a quizzical maitre d' on the other end of the phone, "Barry. Marion Barry. That's right. He's a city councilman. You don't. Okay, thank you."

Instead, he calls this reporter, the Washington Post's city editor, at 11:45 a.m., requesting lunch at 2 o'clock to discuss "general matters," meaning, it turns out, his campaign for reelection, which is already Open Secret No. 1 in the nation's capital. This is a new Marion Barry, Mayor Marion Barry.

He doesn't know what's on the menu. Part is written in French. So he settles for a spinach salad and a steak with no french fries. When the dessert cart is rolled forth, he asks what kind of pudding that is. It's creme caramel, he's told. The mayor says he would like some to go -- to take back to the office. The waiter doesn't understand and brings it in a bowl. The mayor wolfs it down. This is still the same old Marion Barry.

With a surging self-confidence borne of the power of incumbency, the excitement that engulfs a professional soldier when the cry of battle nears and the absence of any certain tough opposition, the mayor of Washington is launching his campaign for reelection. The official announcement will be made in time, he says. "I'm telling people it's a question of when, not if," he says.

He pledges to raise more money than anyone else and to reject campaign contributions from anyone who dares to give to one of his opponents, too. He admits he has made some mistakes in office, but dismisses as folly the findings of polls taken by his would-be opponents, showing him weak and vulnerable.

Even The Washington Post poll had him far behind two weeks before the 1978 election. "The polls are not quite predictable. If they were accurate and right," he says, "Sterling Tucker one of his 1978 primary opponents would be mayor now."

He suggests that the school board might work better if its members were appointed rather than elected as is now the case, and that the city's rising crime rate will be no millstone around his neck.

The Cinderella of '78 who squeaked through the primary on 35 percent of the vote boldly predicts he'll win an absolute majority of 51 percent this time around.

"I don't think any potential candidate can attack my record in terms of our efforts to fight crime, our efforts to clean up the summer jobs program , our efforts to help senior citizens or my handling of the financial situation."

There are many who covet his crown, he says, but they are only politicians on the edge of frustration, as he once was, trapped in a city/county/state where there are only 26 major political offices to hold.

"A lot of the problem of who wants to run for mayor has nothing to do with my performance," he says. "It has to do with the fact that people want to get in office, and if people want to get in office, they have to get in now . . . I was in the same position in '78 that most people are in now."

The current conventional political wisdom, with less than a year left until the crucial 1982 Democratic primary, is that Barry is the person to beat. More than a half-dozen hopefuls, near hopefuls and would-be hopefuls are mentioned as possible challengers -- Tucker, City Council Chairman Arrington Dixon, council members John Ray, Betty Ann Kane, David Clarke, Charlene Drew Jarvis, and John A. Wilson, former secretary of the Army Clifford L. Alexander, former Health and Human Services secretary Patricia R. Harris.

Barry has not expanded his political base much since 1978, and some of it may have slipped, observers say. Barry lent Ray some of his best fund raisers and organizers in 1979 in an effort to help Ray win the race for Barry's old seat on the council. Ray thanked him by scooping up some of the heaviest hitters-- only two, according to Barry; lots more, according to Ray. Barry angered many of his most loyal supporters by giving key jobs in his administration to warriors from other political camps in an effort to unite the Democratic Party.

The mayor says the defections have been minimal, and the gains significant. That will show when he releases a list of supporters. "It's going to be surprising in the quality and quantity," he says.

Let the others talk of being able to raise $500,000 to run against him. "I'll be the only candidate, once I make an announcement and get started, who will be able to raise $400,000. I don't think any other person will be able to raise that kind of money," Barry says.

That's partly, he offers, because of self-interest on the part of donors, big-time businessmen who need the licenses, permits, certificates and development projects that the mayor, his employes and his appointees dole out. "Not that I would ever hold up anything because someone isn't supporting me," Barry quickly explains. "But there is a perception that if you want to cover your bases, you ought to be in good with the mayor."

This is the man who in 1978 attacked Walter E. Washington's administration as "bumbling and bungling." This is the man who shared the dais with Washington Friday night when the former mayor and five others were honored by the United Negro College Fund. "While I think all six of the honorees are distinguished, I am closest to one of them because I know what it's like now," Barry said. "Whenever you find a mayor, you ought to honor him, because running this city is tough, isn't it, Walter." This is the man who admits he has not been perfect, either.

He proposed a new 6 percent tax on gasoline sales. "That was a mistake," he now says. He abandoned it under fire.

When Barry's administration first announced the city's budget crisis, the figures changed from day to day, week to week. "I could be criticized for the early confusion . . . not putting it in its total perspective," Barry says.

The city's water-billing operation is still bumbling about, but he'll solve that problem soon, he says: "By the time the campaign heats up, it'll be an academic issue," Barry vows.

He cannot be attacked, Barry says, on grounds that Washington's crime rate is going up, even though it is: "You can't measure your efforts to fight crime by crime rates . . . What you want people to feel is that the mayor and the chief of police and the police department are doing all they can to make homes safe and businesses secure."

He has battled with the school board over funds, letting its budget rise every year he has been in office, he notes.Cutting it well below what has been asked by the board and once proposing an absolute decrease, he doesn't note.

"The institutional makeup of the school system is such that I can't win that situation," he complains. Since he cannot control how the school board spends its money, he has little power to change the schools through more money. If he urges more money for the schools, taxpayers complain and often don't see results. If he responds to the taxpayers by trying to hold dow funds, hold dowhe is labeled an obstacle to improving public education.

Barry says the solution may lie in a different kind of school board structure. Perhaps the elective school board is an idea whose time has passed, he suggests. After all, he says, the elective school board was authorized in the heat of great agitation for broad home rule. "I think it was like an appeasement program," he says. Now times have changed and a reevaluation is in order.

He notes how the board of the University of the District of Columbia has not reacted to budget cuts with the same degree of antimayor political outcry as the school board, pointing out that UDC's board is chosen by, you guessed it, the mayor.

Sounds like you want to have an appointed school board, comes the response. Barry replies, "I'm not advocating any particular model. But what we have now is not working for the children. You've got natural politicization of the problem. It's highly politicized."

The lunch is soon over. Barry must get back to the office. There is not much time to spend campaigning. "I've been spending my time trying to clean up some things in city government," he says. Besides, he wanted to talk now because this week he is going to Las Vegas for the Sugar Ray Leonard-Thomas Hearns fight, at the request of Mrs. Leonard, who wants the Sugar to have as much support as possible.

Curbside at the Madison, the talk turns to clothes. "I'm still wearing Pierre Cardin," he begins, then checks his label and corrects himself. "I've switched to Jacques Andre," he says, without missing a beat. "I just bought five suits during Raleigh's sale."

"Well," I respond, "that means you're running."

Marion Barry starts chuckling.

I'd have asked him for a lift to the office, but . . . well, maybe I've already been taken for a ride.