Democrat Sharon Pratt Dixon, tapping a citywide desire for a fresh start, won the District mayor's office in a landslide yesterday, while voters resoundingly rejected Mayor Marion Barry's bid for political salvation by denying him an at-large seat on the D.C. Council.

With all 140 precincts reporting, Dixon defeated Republican rival Maurice T. Turner Jr. with 86 percent of the vote, the largest winning share of any mayoral candidate in the District's modern political history.

In the race for two at-large council seats, Democrat Linda Cropp and incumbent Hilda H.M. Mason convincingly defeated Barry, who had hoped the council election would salvage his political career in the aftermath of his drug arrest, trial, conviction and recent sentencing to a six-month prison term.

Democrat Eleanor Holmes Norton overwhelmingly defeated Republican Harry M. Singleton in the race for D.C. delegate to Congress, while council member John A. Wilson (D-Ward 2) breezed to the chairmanship of the District government's 13-member legislative branch.

Democrats Jesse L. Jackson and Florence Pendleton won election to new unsalaried, non-voting positions created by the District to lobby the U.S. Senate for D.C. statehood. Democrat Charles J. Moreland was elected to a comparable lobbying seat in the U.S. House of Representatives.

District elections officials said last night the turnout of 165,466 voters yesterday surpassed the record for mayoral contests set in 1986, when Barry was elected to a third term. Voter registration in the District reached an all-time high this year.

In one of the few upsets of the day, R. Calvin Lockridge (Ward 8), a three-term member of the Board of Education, was unseated by Linda H. Moody. Jay Silberman swept several other candidates to win an at-large seat on the school board.

Voters narrowly defeated a referendum to restore the District's ambitious program of providing shelter to all homeless people, 51 percent to 49 percent. Dixon and other prominent Democrats had urged voters to reject the referendum.

Turner, a career police officer who served eight years as chief before his retirement in mid-1989, conceded defeat shortly before 10 p.m., saying the campaign "certainly has broadened my horizons."

"I'm not ashamed of the race we ran," said Turner, who had telephoned congratulations to Dixon.

Dixon, exulting in her victory a few minutes later at a Northwest Washington hotel, told a cheering crowd of supporters, "The people of the District of Columbia have spoken and they've sent a message clearly, unequivocally and almost universally . . . . They have said it is time to clean house."

"My heart is full," Dixon added. "D.C., I want you to know I'm not going to let you down."

Dixon's appeal cut across lines of color and class, and extended to all age groups, according to exit polling conducted yesterday for The Washington Post. She even beat Turner among that part of the electorate he needed to hold -- Republicans -- the poll found.

About half of those interviewed said they favored increasing taxes to help solve the District's escalating financial crisis, a sentiment that could help Dixon as she grapples with what next year could be a $100 million deficit.

In the latter stages of the campaign, Dixon relaxed her once-firm pledge against new taxes by saying she might sign a tax package if the D.C. Council sends her one.

Dixon's ascension and Barry's defeat mark the culmination of an extraordinary year, which was only 18 days old when the mayor was arrested at the Vista hotel in a FBI drug sting.

All summer, as the city was transfixed by Barry's personal and political drama, polls showed Dixon trailing four other Democrats in the primary field, but with a simple pledge to "clean house" she rode a wave of voter discontent and captured her party's nomination in the September election.

The voter demand for change appeared to be just as strong and sweeping yesterday. As Frances Smith, a 70-year-old federal government retiree, described it outside her polling place in Northwest Washington, "We need a new thing."

Dixon's Jan. 2 inauguration as the District's third elected mayor will likely propel the 46-year-old lawyer and former utility company executive to the forefront of black office-holders in this country, as well as women politicians, who fared quite well in the District yesterday.

Sharon Rodine, president of the National Women's Political Caucus, hailed Dixon's victory last night, saying she "will bring a new style of leadership much needed in this nation's capital."

Rodine added that despite an income tax controversy that disrupted Norton's campaign, District residents had given the Georgetown University law professor and former Carter administration official a vote of confidence for her "integrity and illustrious career as a women's rights and civil rights advocate."

For Barry, the vote last night was a political verdict after a wrenching, summer-long trial that ended with one guilty verdict -- for a misdemeanor offense of cocaine possession. Barry was found not guilty on another charge and the jury reached no verdict on 12 other charges.

Barry carried only one of the District's eight political subdivisions, Ward 8, the poorest in the city and the one with the highest percentage of black residents. Even there, the mayor mustered just over half of the overall vote. Voters could choose two candidates in the at-large council race.

Cropp and Mason led Barry throughout much of the city, although Barry did better in the predominantly black areas of the city, in Wards 4, 5, 7 and 8.

In Ward 3, a predominantly white section west of Rock Creek Park, Barry garnered a scant 2 percent of the vote, in contrast to 76 percent for Cropp and 64 percent for Mason. Barry also fared poorly in Wards 1 and 2, which also have large proportions of white residents.

The anti-Barry mood in Ward 3 was expressed by Henry Eakins, a 58-year-old Republican who said he voted for Cropp, a Democrat, and Mason "to get rid of Barry."

"That's the only reason," Eakins said.

At the same time, some voters who said they held affection for the three-term mayor decided against him in the end.

"I think Barry's a good man, but I didn't go with him this time," said Cardoza Bigby, who voted in the mayor's home precinct in Ward 7 of Southeast Washington. "I sure wish he would have passed, rested up a bit and just kept a watchful eye on things."

Dixon had several advantages going into yesterday's election, including a long record of service in the local and national Democratic Party, which in the District enjoys a nearly 4 to 1 registration edge over Republicans and independents.

She also had relatively little difficulty raising money, in contrast to Turner, who carried large debts throughout the campaign and may have ended the race with obligations exceeding $100,000.

Turner may have been hurt by his years as police chief. Throughout the race against Dixon, he was forced to answer questions about what he knew of Barry's illegal drug use and defend his own record as chief during a period when the D.C. homicide rate reached record levels.

"Mr. Turner has had an opportunity to do something about crime as chief and he did not do anything," said Barbara S. Lucas, a retired teacher who voted yesterday at Bertie Backus Junior High School in Northeast, in one of the heaviest voting precincts in the city.

Dixon sought on several occasions to link Turner to the most conservative elements of the national GOP, and he responded that he was at odds with that wing of the party on abortion rights, D.C. statehood and other issues.

Turner, meanwhile, had been publicly courted by the White House. President Bush, who had helped recruit Turner to the GOP fold, and Barbara Bush campaigned with him, while Vice President Quayle appeared at one Turner fund-raiser in Northwest Washington.

The Republican National Committee sent a high-ranking campaign operative, James King, to run Turner's effort.