Gov. James S. Gilmore III suffered a double political setback today when one candidate he endorsed lost a Republican primary in Prince William County and another failed in an expensive race in the governor's home district.

Gilmore took some consolation in the victories of the two other Republican primary contenders he endorsed, including one for a House seat in Loudoun County.

But risking and losing political capital in the most intensely watched primary -- between two Richmond Republicans in his own back yard -- was painful to Gilmore and his administration, and Democrats were crowing about it tonight.

"Today's results are a devastating defeat for Governor Gilmore," said Del. Kenneth R. Plum (Fairfax), chairman of the state Democratic Party. "Even voters in his own party's primaries have rejected the governor's efforts to establish a rubber-stamp Republican legislature controlled by him."

Six of the 11 legislative primaries for Democrats and Republicans were in Northern Virginia. In Loudoun County, Del. Richard H. Black (R), of Sterling, running with Gilmore's backing, handily won renomination against David G. McWatters, a member of the Loudoun County Board of Supervisors.

Gilmore was not as successful with his candidate G.E. Buck Waters, who was beaten by antiabortion activist Robert S. FitzSimmonds in a Prince William County primary race for a state Senate seat held by a 24-year Democratic incumbent.

Elsewhere in the region, Carole Herrick won the Democratic primary in House District 34 in McLean, setting up a rematch of her 1997 challenge of Del. Vincent F. Callahan Jr., the ranking House Republican and co-chairman of the House Appropriations Committee. Herrick defeated John W. Foust, also of McLean.

In Dale City, Virginia Stephens defeated G. Gary Jacobsen for the Democratic nomination in House District 51. In the fall, Stephens will face Del. Michele B. McQuigg, who was chosen in a special election in January 1998.

In another Democratic contest, Denise M. Oppenhagen defeated Billy Gray Tatum for the chance to unseat Del. Robert G. Marshall (R-Prince William). Oppenhagen had argued that Marshall was wrong to side with Gilmore in the Hugh Finn right-to-die case last year.

In the 27th state Senate District, which includes a portion of Fauquier County, Sen. H. Russell Potts Jr. defeated Mike McHugh for the Republican nomination.

In Norfolk, Del. William P. Robinson Jr., the ranking member of the Legislative Black Caucus, defeated former Circuit Court judge Luther C. Edmonds, who may face a retrial on charges that he pistol-whipped his former friend Robinson after the election two years ago. A mistrial was declared last month in the case, in which Edmonds was charged with malicious wounding, using a gun and wearing a mask.

Gilmore is waging a tenacious seat-by-seat campaign in the legislative elections this fall, which could finally tip the General Assembly in his favor and give him a mandate for his proposals next year.

The hot race of the spring season was here in Richmond, where insurance executive Ruble A. Hord III drew the highly publicized support of Gilmore, the capital's congressman and the state attorney general in the nastiest GOP family feud in years. Hord lost to Del. Anne G. Rhodes.

With Gilmore's help, Hord waged what probably will turn out to be the most expensive legislative primary in Virginia history, at a cost of roughly $500,000 for the two candidates.

The race between Hord and Rhodes, who has been a thorn in Gilmore's side since he swept into office in the 1997 governor's election, will reverberate far beyond her part-time legislative job, which pays about $18,000 a year. Not only was it the big-money race of the primary season, but it marked an unusual -- and potentially risky -- intervention by a sitting governor into one of his party's internal fights.

"You can watch the world go 'round, or you can try to make a difference," said Gilmore's press secretary, Mark A. Miner.

After her victory speech at a Richmond hotel, Rhodes said she was disappointed by the GOP infighting this spring, saying it was a waste of resources.

"I'm sorry that happened, because I don't think it was good for the party," Rhodes said. "I'm a moderate Republican, and I think I represent an awful lot of people in the party."

In a statement tonight, Gilmore congratulated Rhodes, saying, "Now is the time for Republicans to unite."

In Loudoun, Gilmore's political action committee pumped thousands of dollars into Black's campaign and telephoned voters on Black's behalf.

Black said his renomination was a validation of his conservative agenda.

"I think [voters] feel very positive about our overall family-values approach," Black said. "They want a community that's kept free of crime, vice and corruption."

He said that Gilmore's involvement in the campaign was appropriate because they work closely together.

"What my opponent needs to understand is the reason we have eliminated the car tax, the reason we have built the roads and the reason we have brought back money for the schools is a team effort in which I have worked very closely with the governor," Black said. "It's a long-standing relationship where we have jointly worked to advance the interests of the commonwealth."

Black had pressed the legislature to impose more restrictions on abortion. As a member of the Loudoun County Library Board, he was the author of a plan that required the use of filtering software to prevent young people from getting access to pornography on the Internet.

McWatters had called for more spending on education. He also portrayed himself as more of a centrist, saying Black's conservative agenda was out of touch with Loudoun voters. He took issue with Black's support of a measure that would have allowed residents with permits to carry concealed weapons into restaurants and bars.

McWatters said that he was saddened by the results and that Gilmore's involvement cost him the election.

"I'm disgusted with Governor Gilmore, and I'm ashamed of him," McWatters said. "He's a bully, and he's a tyrant. . . . I would question the governor's motives, and why do we have campaigns at the local level if the governor is going to go around handpicking delegates? It seems to me like we're going from a democracy to a monarchy."

Black will face Democrat Kelly Burk in November. She issued a statement last night saying Black was elected by a group of supporters who are not representative of the district.

Staff writers Donald P. Baker, Justin Blum, Dan Eggen, Michael D. Shear and Graeme Zielinski contributed to this report.

Northern Virginia Primary Results

Unofficial results from the primaries for state and local offices in Northern Virginia:

Democratic Primaries

House District 13 (Prince William)

Billy Gray Tatum 331 39%

Denise M. Oppenhagen 510 61

House District 34 (Fairfax)

John W. Foust 464 41%

Carole L. Herrick 658 59%

House District 51 (Prince William)

G. Gary Jacobsen 168 19%

Virginia Stephens 710 81

Prince William: Clerk of Court

Joyce M. Sowards 1485 62%

Louis Ginesi Dominguez 901 38

Republican Primaries

House District 32 (Loudoun/Fairfax)

Richard H. Black 2238 59%

David G. McWatters 1533 41

Senate District 27 (Fauquier)

H. Russell Potts Jr. 7971 62%

Mike McHugh 4859 38

Senate District 29 (Prince William)

G.E. Buck Waters 2610 48%

Robert S. FitzSimmonds 2784 52

Prince William: Gainesville Supervisor

Martha W. Hendley 1211 41%

Kevin Paul Childers 498 17

Edgar S. Wilbourn III 1222 42

Fauquier County: Cedar Run District Supervisor

J. Mark Rohrbaugh Jr. 578 42%

Raymond E. Graham 791 58

Fauquier County: Lee District Supervisor

S.L. "Serf" Guerra 296 31%

Sharon Grove McCamy 657 69

Fauquier County: Clerk of Court

John Marshall Cheatwood 1055 23%

Gail H. Barb 3476 77

Stafford County: Commissioner of Revenue

Kenneth Mitchell Not available

Scott Mayausky

Stafford County: Sheriff

Charles Jett Not available

G.W. "Jerry" Tolson

CAPTION: Richard H. Black, left, greets voter Luke Boyd. Black handily won the Republican primary for his House seat.

CAPTION: In Leesburg, David G. McWatters, a Loudoun supervisor seeking the GOP House nomination, talks to voter MarthaBelle Jones, who is holding literature from McWatters's opponent, incumbent Richard H. Black. McWatters lost the primary race to Black.