With candidates sparring almost nightly at political forums, a battle for five House of Delegates seats from southern Fairfax County has turned into one of Norhtern Virginia's most acrimonious contests this fall.

And, in contrast to their behavior two year ago, Republicans in the 19th District race are attacking Democrats, instead of each other.

The 10-candidate race, one of several local and General Assembly contests to be decided in the Nov. 6 general election, has particularly spotlighted the political barbs of Republican Del. Robert L. Thoburn. Considered the most conservative legislator in the General Assembly, Thoburn, 50, is a favorite target of his Democratic opponents -- and he responds in kind.

"The Democrats keep talking about how we're being taxed to death, but just who has been in control of the legislature and the County Board?" he asks at every voter gathering.

Thoburn, a minister and church school administrator who is seeking his second term as delegate, is being challenged head-on for his opposition to the Equal Rights Amendment, to collective bargaining for public employes and to proposed tax increases to operate Metro.

Along with Del. Robert E. Harris, the second of three incumbent Republicans in the race, Thoburn has been under persistent attack for voting against a proposed one-cent sales tax to fund the subway system.

The strongest criticism has come from two Democratic candidates, David L. Temple and Charles E. Kaufman, who are making their first bids for elective office.

"Thoburn got in last time because the Republicans didn't know how out of step he was, even with them," said Kaufman. "I'm trying to show he's not a kindred spirit, and that he's got a record totally unrepresentative of Northern Virginia."

Del. Gladys B. Keating, the only incumbent Democrat in the race, has heard Thoburn tell audiences that some of the bills she got passed were "frivolous." She has found herself fighting back -- if only in self-defense.

"I don't believe in attacking someone else, but for a man of the cloth to twist the truth the way he does . . ." she complains, her voice trailing off.

All 10 delegate candidates showed up for a political function recently at the Greenbriar West Elementary School. Each was allowed five minutes to win over votes from an audience of about 120.

Thoburn, who used his time to tout his conservative credentials, expects that his following is large enough to fend off the women's rights, labor and teacher groups that have targeted him for defeat.

"Most of them are the same people," said Thoburn. "They (pro-ERA organizers) have supposedly identified 12,000 votes against me, but it's only stirring me up to campaign harder."

In another example of a head-on campaign combat, Democrat Beverly J. Schwarz recently attacked one of her Republican opponents, Lawrence D. Pratt, for failing to indicate on his financial disclosure form the extent of his involvement with the Gun Owners of America.

Schwarz, saying she was "appalled by the apparent discrepancies" in Pratt's filing, said he listed his consulting firm, Larry Pratt and Associates, as his only economic interest. Actually, Schwarz charged, Pratt is a registered lobbyist for the Gun Owners of America, a group that is opposed to gun control, and that Pratt can be reached by telephone at the group's offices in Washington.

Nothing that his campaign contributors include those opposed to gun control, Pratt said he divides his time almost evenly between Gun Owners of America and a group he heads known as American Marketing Consultants, Inc. He added that he was retained by the Gun Owners through Larry Pratt and Associates.

Pratt accused Schwarz of trying to develop another issue to help her own campaign. "Her (previous) city planning experience in New York is not the greatest recommendation here," he said.

Schwarz, 31, is making her first bid for elective office. Once a Staten Island city planner, she thinks her experience can "help force development to be done the way you want it." A former legislative assistant to a congressman, Schwarz said she would know how to do the committee work needed to win support for legislation to help Northern Virginians get "back a fairer share" of the tax monies sent to Richmond.

Pratt, 36, like other candidates, questions the need for sales tax for Metro. He also opposes the Equal Rights Amendment.

Pratt has chided Democrats for "ineffectiveness" in getting more state funds for the region. He has promised to be more responsive to the problems of traffic congestion and has promoted programs designed to provide restitution to victims of property crimes.

Other candidates in the 19th District race:

Charles E. Kaufman: A former aide to Fairfax County supervisor Joe Alexander, Kaufman, 27, has been active in Democratic politics in the county. An advocate of greater flexibility in taxation to relieve the burden on property owners, he owns a direct-mail advertising company.

He repeatedly challenges those who oppose a sales tax to fund Metro. A bill on that issue, defeated by the General Assembly last session, actually was "a homeowner's relief" bill because it gave localities a taxing option, Kaufman argues. He also notes that the Metro funding bill was not a partisan issue in Northern Virginia because Thoburn and Harris were the only Republicans in the region to oppose it.

Gladys B. Keating: Long involved in civic association work, Keating, 56, is completing her first term in the House. She ran three times before winning her present seat but, as the only incumbent Democratic delegate, now has a strong following in her district.

After successfully sponsoring several consumer protection bills in Richmond, Keating continues to support some of the measures "that didn't get through." One she mentions frequently is legislation to establish the concept of marital property so homemakers will get as much protection during divorce proceedings as wives who work outside the home.

Jane M. King: A former history teacher who also has worked as a legislative aide in Richmond, King, 38, is seeking public office for the first time. A Democrat, she hopes to help Norhtern Virginians fight inflation and to increase the involvement of women in state government.

"The attitude toward Northern Virginia in Richmond is that we are rich and able to take care of ourselves," said King. "And women are to be seen, possibly appreciated, but certainly never heard."

David L. Temple: An educator and principal of the Dunn Loring Center for Emotionally Disturbed Children, Temple, 31, is the only black candidate in any of the region's General Assembly races. If elected, he would become the first black to serve in the legislature from Northern Virginia.

Acknowledging that most of the candidates, with one or two exceptions, have similar positions on local issues, Temple stresses his value as a native Virginian and a longtime Democratic party activist. He would like to limit taxes, control utility costs and restructure representation in the legislature by creating single-member districts.

Warren E. Barry: With 10 years in the assembly, Barry, 46, is the senior legislator from the 19th District. An incumbent Republican who has his own property management and travel-service firm, he can recite a list of bills he has shepherded through the House and Senate. One measure -- passed while Barry was a smoker -- raised the tax on tobacco to avoid raising taxes on food and property.

Generally, Barry cautioned, Northern Virginians should be electing legislators "who can self-discipline themselves and say 'no' to too much government."

James H. Dillard: Knocked out of his House seat two years ago after a bitter Republican primary battle, Dillard, 45, had served as a delegate for six years. Thoburn's ultraconservative backers were Dillard's undoing in 1977, but all the Republicans are being much more conciliatory for this election.

A high school government teacher, Dillard's concerns in the legislature were soil erosion, consumer protection and expanding citizen access to meetings of public officials. He would like to see Norhtern Virginia get a fairer share of its tax dollars by including "a cost-of-government formula" in the distribution of tax monies.

Robert E. Harris: Completing his third term, the Republican incumbent, 43, is a business executive. A member of the House Committee on Roads and Internal Navigation, Harris described himself as "the point man" on that panel in fighting past attempts by Arlington and Alexandria to stop completion of I-66.

As a member of the Northern Virginia Transportation Commission, Harris has pushed for improvement of secondary roads in the county. But he opposes any Metro funding bill that would require a sales tax.