"If you like my father, you'll love me," promised John Thoburn when he announced plans to run for the Virginia Senate. Fairfax County political leaders knew exactly what he meant.

Thoburn, the 22-year-old son of ultra conservative Del. Robert Thoburn (R-Fairfax), hopes to follow in his father's legislative footsteps, and he has adopted the same blunt campaign style that helped put the elder Thoburn in office two years ago.

"I don't believe in giving liberals a free ride - I believe in beating them," said Thoburn recently, reffering to the November challenge he hopes to make against Senate majority leader Adelard Brault (D-Fairfax).

The same holds true for Thoburn's opponent in the June 12 Republican primary, Cynthia Newman, an attorney and former Secretary of the Commonwealth.

"She's too liberal for me," complains Thoburn of Newman, 57.

By liberal, Thoburn means that Newman supports the Equal Rights Amendment banning discrimination on the basis of sex. He opposes the ERA and thinks an advisory referendum on the issue would kill it the same way a referendum killed plans to allow pari-mutuel horse race betting in the state.

Thoburn, who graduated from his father's Fairfax Christian School and now works there part-time while studying for an economics degree, also opposes abortion, collective bargaining for public employes and any special tax to raise funds for the Metro system.

"I think the people who go to work in Washington should be the ones to pay," Thoburn said. "It doesn't help most people in the suburbs."

Thoburn expects that his father's followers in the 34th Senate District, which includes Fairfax City and the central portion of the county, will work to his adavantage in the primary. But the two do not share the same political jurisdiction.

Newman, on the other hand, is counting on her years of service to the state GOP and her long involvement in party politics in the county to help her capture the Republican nomination.

"I thought about challenging Brault four years ago, but I wanted to wait until I got all my kids off to school," said Newman, who owns her own travel agency here. She ran for the House of Delegates in 1953, coming in fourth out of four candidates. She served as Secretary of the Commonwealth under Republican Gov. Linwood Holton between 1970 and 1974, and in that capacity kept records of all lobyist registrations, issued a list of official state government office-holders and handled communications between Virginia and other states.

Newman reaffirmed her longtime ERA support, but said she does not believe in "one-issue races." She favors right to work laws and opposes collective bargaining for public employers, although she would not mind permitting them to "meet and confer" on the terms and conditions of their employment.

Both Republican contenders have started attacking Brault in preparation for the November general election.

Thoburn complains that Brault, though opposed to abortion, nevertheless supports Democratic officeholders who will not work for a Constitutional amendment banning such procedures. Newman says the 70-year-old veteran legislator "has not demonstrated the qualities of leadership for his district in terms of what Northern Virginians are most concerned about."

Newman said she plans "not to just be a figurehead in Richmond," but Thoburn said he is more familiar with the General Assembly's workings than Newman by virtue of his job last session as his father's legislative assistant.

"My primary opponent had a political patronage job some years ago, but she is not really in on things now," he said.

Newman, who has been campaigning hard, said voters in her district are universally interested in the issues of "traffic and taxes." Next, she said, comes an overall concern with socalled women's issues such as divorce and rape law reform.

Thoburn, saying he supports divorce and rape law reform, regards the ERA as "a major issue" in the campaign. He also would work for legislation to force convicted criminals to make financial restitution to their victims instead of being incarcerated. Additionally, he supports allowing voters to seek tax reforms through initiatives and referendums. CAPTION: Picture, JOHN THOBURN . . . he believes in "beating liberals"