Democrats running for local offices in Fairfax County successfully resisted an electoral assault by Republicans yesterday, bucking the trend in statewide races and increasing their hold on the Board of Supervisors to a 7 to 3 majority.

First-time candidate Catherine M. Hudgins, the former aide to Democratic Board Chairman Katherine K. Hanley, ousted two-term GOP Supervisor Robert B. Dix Jr. in a race that Hudgins said would be a referendum on Dix and his management of growth in the Reston and Vienna areas.

Hudgins, a political novice and the first African American on the board, stunned observers with a victory over Dix, a longtime politician who had received much of his $200,000 war chest from high-tech executives in his bid for a third term on the board. Hudgins raised about a quarter of that.

"The voters wanted someone to listen and work with them on the critical problems of growth, transportation and education," Hudgins said yesterday. "They want us to take a look at how we grow."

Fairfax Democrats also ousted the county Republican sheriff, Carl R. Peed after a campaign featuring attacks and counterattacks by Peed and his Democratic challenger, former sheriff's deputy Stanley G. Barry.

In the School Board races, it appeared that the Democrat-controlled board would retain its majority, winning seven of 12 seats. School Board races are officially nonpartisan, but both major parties endorsed full slates this fall.

The party did lose one of its leaders on the board. Unofficial returns showed board Vice Chairman Mark H. Emery (At Large) losing narrowly to Republican-endorsed Rita S. Thompson. Two other incumbents--one Democrat and one Republican--also lost their seats.

Voters shouted an overwhelming "yes" to school officials, who had asked for approval of $297.2 million in bonds to be used for construction of new schools and renovation of existing buildings.

On a day when Republicans elbowed their way to a slim majority in both houses of the General Assembly, Democrats in Fairfax County savored the sweetness of successes.

"The Republicans put a lot of money into a losing campaign," said County Democratic Committee Chairwoman Emily Miller. "Fairfax County will be a big embarrassment for the Republicans. I am so proud to be chairman of this committee."

Miller crowed that the Fairfax GOP's oft-stated strategy to take away Hanley's Democratic majority on the Board of Supervisors--to make her the "Queen of Nothing"--had failed.

"Kate is still Queen of Fairfax," she said.

Hanley easily won her race against two independents and a Libertarian. Five supervisors--three Democrats and two Republicans--were unopposed.

Control of the Board of Supervisors was seen as critical by members of both parties as the supervisors prepare to select a new county executive this month. The outcome will shape future battles over tax rates, education spending, revitalization of older buildings and reform of the county's 11,000-employee bureaucracy.

"It will help set the agenda for the next decade. The education agenda, the transportation agenda, the public safety agenda," said Fairfax Supervisor Gerald E. Connolly (D-Providence).

The Democrats will now have strong control of the board in 2001, giving them the power to redraw the supervisor districts after the 2000 Census. That could give them a lock on power for the next decade.

Republicans had privately said it would be tough to gain a majority. But Dix's loss came as a major blow, especially to the high-tech business community, which has made the Dulles Corridor in the Hunter Mill District its home during the past several years.

The business community was behind Dix, who they characterized as a wholehearted supporter. Yesterday, they were stunned by his loss to a relative unknown.

Edward H. Bersoff, a high-tech executive and former chairman of the Fairfax County Chamber of Commerce, said he was disappointed with Dix's defeat but did not believe that the tone of the board would change as a result of the Democratic gains.

"Bob has been a good friend of the business community for some time, and while some folks had difficulty with his style, he was effective in what he did," Bersoff said.

Bersoff added, however, that "some truce" had been reached by the county supervisors and the business community in recent years and he didn't foresee that atmosphere changing with another Democratic supervisor.

"I've been heartened by things that are less knee-jerk and more thought through by the board," Bersoff said. "I don't think things will change much."

Connolly, who frequently clashed with Dix on the Board of Supervisors, said voters were tired of Dix's mercurial style.

"The voters of Hunter Mill were tired of the tone of incivility and intolerance for different points of view that had been set by Mr. Dix," Connolly said. "They clearly want a supervisor in whom they can be proud."

Rep. Thomas M. Davis III (R-Va.), who had funneled thousands of dollars into local and state races, said he was disappointed by the failure of Republicans he had supported to gain or keep seats on the county board.

"Election nights are always bittersweet," Davis said. "You don't win them all."

In the Dranesville District, which includes McLean, Great Falls and part of Tysons Corner, Democrat Barbara Phillips had attacked incumbent Republican Stuart Mendelsohn for approving a developer's plan to build upscale town houses on the beloved Evans Farm property.

Voters chose to leave Mendelsohn in office yesterday, sending the message that concern about Evans Farm, while intense, was limited to a relatively small group of activists.

Voter Kate Madison, 60, a therapist from McLean, said Evans Farm was not a deciding factor for her, and she would continue to support her supervisor, the only Republican she voted for. "I wasn't for Evans Farm being saved for the McLean yuppies," she said.

In the Mason District, incumbent Democrat Penelope Gross successfully fought off former GOP supervisor Christine R. Trapnell in a race where voters were asked to choose between two women who each touted their records of constituent service.

The race in part focused on the influx of immigrants to the Seven Corners and Baileys Crossroads area, and complaints among longtime residents about the impact the newcomers are having on traffic, revitalization and crime.

And in the Lee District, where Republican R.M. "Bob" Jones had sounded almost like slow-growth Democrats elsewhere in the county by attacking incumbent Kauffman for allowing growth without investing in roads, Kauffman won easily.

Although Republicans picked up one seat on the School Board, the win is not likely to make much difference to the board's agenda. Of the election's 12 winners, the majority support the initiatives of the current board and Superintendent Daniel Domenech.

In the Braddock District, Judith T. "Tessie" Wilson, the Republican-endorsed candidate, defeated Democratic incumbent Ilryong Moon. In Springfield, newcomer Catherine A. "Cathy" Belter, who was endorsed by the Democrats, ousted Republican Carter S. Thomas, one of the most conservative members of the board.

Democrats held onto the Mount Vernon seat, the only open seat on the board, with the election of Isis Castro.

CAPTION: Catherine M. Hudgins is embraced by supporters at Democratic election headquarters at Tysons Corner Sheraton Premiere. Hudgins beat two-term GOP Supervisor Robert B. Dix Jr.