They agree on the enemy (incumbent Rep. Herbert E. Harris) and the issue (inflation) and ideologically they range from conservative to ultraconservative.

And so Robert Harris, John F. Herrity and Robert Thoburn seek to emphasize the differences in their strategies and style as they traverse Virginia's 8th Congressional District in search of votes for next month's Republican primary.

There are still five weeks to go before the votes will be cast. So far, this primary has been a somewhat desultory affair, a solitary exercise where the key to victory is not the public rhetoric - which hasn't been much warmer than the weather this spring - but the careful targeting of the candidates, individual constituencies.

Primary voters are breed apart from those who go to the polls in a general election and, like miners panning for gold, the candidates sift the precincts looking for nuggets for support - the party stalwarts hungry for a winner this time around, or the voters whose choice turns on a candidate's stand on a single issue, like gun control or abortion, or the hard-core supporters of a past campaign.

With an eye toward party unity in the general election, the candidates have so far left each other alone, aiming their volleys at the incumbent rather than each other. "We have been," Thoburn says, "like ships passing in the dark."

There are times, however, in their rambles through this far-flung district, when the three men do share a podium. At a recent meeting of the Greenbriar Republican Club in western Fairfax, the members lost no time in getting to the heart of the matter: winning in November.

"I want you guys tell us specifically how you're gonna take Herb Harris in the fall," said one man who had just listened to each of the candidates give his standard five minutes worth of philosophy, catch phrases and credentials.

The candidates leapt to the question like salmon to the spawning grounds.

Well, said Herrity, chairman of the Fairfax County Board of Supervisors, "I'm certainly not going to debate Thomas Aquinas, Thomas More, Aristotle and Plato with him. It's going to be a nitty-gritty campaign. You have to expose his record for what it really is, but it's not going to be a negative campaign. The primary emphasis has to be on what you are going to do if you're elected."

Thoburn, however, seems to brandish the negative aspects of his approch. A first-term General assembly delegate, ordained minister and self-proclaimed millionaire, Thoburn came rushing out of political obscurity two years ago to make his first bid for the Republican congressional nomination, and lost by less than 200 votes.

What you have to do, Thoburn told the fewer than two dozen people gathered at the Greenbriar Community Center; is "to polarize the voters on the issues. And believe me," he says, "I can polarize the voters on the issues."

Thoburn mentioned with pride that he was "hauled before the Fair Campaign Practices Committee in my last race" (for the General Assembly), just as he gleefully recalled later that night that defeated Virginia gubernatorial candidate Henry E. Howell once called him "a Siamese twin to a caveman."

"Look at my voting record in Richmond," Thoburn said. "I voted yes on some stuff, a lot of trivial stuff. But I voted no on all the really important stuff."

Robert E. Harris, a third-term delegate to the General Assembly, emphasized his knowledge of "the latest techniques" in the art of getting elected, but he too hinted darkly of the incumbent's divergence from what he considers "mainstream" sentiment in the 8th District and talked of how he will "expose" Rep. Harris "for the fraud he really is."

"Wow," said one Greenbriar Republican in wonder as the meeting ended. "I'm a New York Republican myself. We just don't make 'em that conservative up there."

By now, the candidates were back in their respective cars, curving along the arcs and exits of I-66 and I-495 and I-395, past the quarter-acre lots of Fairfax subdivisions and the glass and concrete of Alexandria's Condo Canyon to a meeting of that city's Republicans. Again the speeches, fast-paced pitches on electability and The Enemy, with many of the same questions asked, most of the same answers given.

Apart from these polite, almost ritualized joint appearances before the most active elements in the Republican Party, the contenders go their own way in searching for other votes that could make for a margin of victory.

Herrity is running, for instance, with the backing of many of the party regulars, a full-time professional campaign manager, a steady stream of press releases and an emphasis on personal contact with the voter through phone calls and house calls.

"I only know one speed to run," Herrity said, "and that's flat out," but one of his opponents, Robert Harris, is campaigning in a lower gear, a testimony, he said, to his own skill as a vote getter.

"Very frankly, in all candor, in a primary there is only so much you can do," Harris said. "The other guys who haven't run as often as I have probably don't understand how much wheel spinning you can do. The trick is to get all the right bases covered."

Covering the bases, Harris contends, means allowing for the fact that "most of the people out there don't even know there is a primary. You have to focus in on the people who normally vote in a primary. That's called your voter ID system."

Thoburn, meanwhile, has a system of his own that he thinks will win him the primary, one that at this point includes an unlisted telephone number in his campaign headquarters and a reluctance to give out his campaign schedule.

Instead, the campaign is run out of the private school he owns and operates and much of the time, he said, is spent "organizing" and training volunteers. "If we win," Thoburn said, "We'll move out and get more spacious quarters."

Although Thoburn cruises for votes in a black Cadillac, he is aware that most of his operation has little of the glamor that is part of the public image of a campaign. "We sound like a bunch of amateurs, maybe, but we run a sophisticated campaign," he said.