WHAT A DIFFERENCE a year makes. Just 12 months ago, Washington's mayor-elect, Sharon Pratt Dixon, was entering a campaign against (as it was expected) Marion Barry, without support or big financial backing or the company even of competitors for the job. When the mayor got in trouble and as the field of Democratic candidates to replace him widened, Mrs. Dixon, the first one in the race, was, by consensus, sent to the back of the line. She nevertheless persisted in her clear message: that the District voters were ready and eager for change, that they understood and deeply objected to the moral squalor into which Mr. Barry was dragging his office, his party, his government and inevitably the city itself. Her smashing victory, first in the primary and then, Tuesday night, in the general election belies the terrible slander of Washington that has unfairly gained such wide national currency -- the slander which holds that the residents of this city were somehow implicated in the doings of the mayor, that they did not object to and would never repudiate them, that they thought the status quo was just fine. It was never true, but that fact was never so clear as it became at around 9 o'clock Tuesday night.

The election of Hilda Mason and Linda Cropp to the at-large D.C. Council seats and their defeat of Mayor Barry for the job reinforces this truth. And together it all goes a certain distance not just to dispelling the myths about the District and regenerating people's pride in their city, but also to persuading the federal government -- both the legislative and executive branches -- that the District of their imagination is not the real one, and that the real one needs and deserves more help. This help, incidentally, involves more than merely bringing the federal payment to its fair level. There are many other obligations to the District that it has neglected far too long.

Mrs. Dixon will clearly be looking to the new D.C. Council and the new delegate to the House for support in the formidable but crucial mission of convincing the federal government of these things. But she herself has rightly stated over and over again that there is a local government overhaul necessary to strengthen the city's case in its dealings with the administration and Congress. Her pledge to undertake this overhaul was resoundingly -- as she said, all but "universally" -- seconded by the voters of every part of the city. The reconstituted council, to which, fortunately Marion Barry was not elected, will be led by John Wilson, a man who understands this and can be a great partner in the enterprise -- if they both choose to attack it cooperatively. We hope they do. It was, by the way, welcome and gracious of former police chief Maurice Turner, whom Mrs. Dixon defeated, to offer his help in what he too considers a new and better day for his native city.

Help for Mrs. Dixon on the Hill will be more complicated. Eleanor Holmes Norton, who won her contest handily, will be dealing not only with the House but also with the "shadows" elected to lobby the Senate and the House for statehood -- Jesse Jackson, Florence Pendleton and Charles J. Moreland. No one knows how these interrelationships will work, especially since Mrs. Dixon herself has many working connections with key people in both bodies and will no doubt herself want to speak for the government she will be responsible for and running. We have our own often expressed reservations about the shadowships, about Mr. Moreland's prolonged federal and state tax "protest" and Mrs. Norton's failure to clear up her own D.C. tax problems; but there is no question that all of these emissaries to Congress are strongly committed to a better, fairer deal for the city. As Mrs. Norton said on election night, when the returns from Virginia's 8th District came in "Thank you, Northern Virginia": the absence of newly defeated Rep. Stan Parris from the District Committee should be a huge help. (It should be an even huger help to Northern Virginia, for a variety of reasons voters there understood well enough to replace him with Jim Moran.)

Mrs. Dixon has also said that rescue of the city's troubled school system is a prerequisite of revitalizing the city -- not to mention a moral duty in itself. A District mayor has very limited powers in this regard, but the new government is indeed fortunate to have a vastly improved school board to work with as a result of these elections. The addition of Jay Silberman, Linda Moody and Sandra Butler-Truesdale and the departure at long last of R. Calvin Lockridge are pure good news.

The rejection of Referendum OO5 by the voters should help ease the financial pressures on the District somewhat. But that is only a small beginning. There are enormous -- and painful -- steps to be taken in this connection. Dealing with the District's financial troubles is going to require energy, seriousness, political courage and political skills as well, because no program can work unless the public is brought along. Both the mayor-elect and the electorate that did so many good things on Tuesday seem to us ready to tackle the job.