Brace yourself. Local politics in Northern Virginia is about to enter the media age.

With a Washington Post poll showing Fairfax County Board Chairman John F. Herrity (R-At Large) trailing Supervisor Audrey Moore (D-Annandale) by at least 12 points just five weeks before Election Day, the two candidates will be raising the curtain on major advertising campaigns in the coming days.

Herrity, who already has aired two radio spots and a television ad -- all designed to bolster his public stand- ing -- is expected to concentrate his energies this month on attacking Moore -- or, in the parlance of media consultants, "raising her negatives."

Herrity's strategy stems in large part from his problems, particularly the steady stream of bad publicity he has received for more than a year because of his driving infractions and a misdemeanor conviction for violating a state public disclosure law. Those misdeeds, and the ensuing news reports, have driven up his negative rating -- as perceived by the 1,146 registered voters surveyed by the Post -- to about 38 percent.

In contrast, only about 15 percent of the respondents rated Moore negatively, while a large number said that they did not know much about her. According to political analysts, that gives Herrity an opening: to increase Moore's negatives with voters -- many of them recent arrivals in the county -- who do not know her.

Will it work? There are at least two schools of thought.

One is that undecided voters, livid at the county's traffic jams and the state of the roads, will vote against whichever candidate they believe is to blame. Because Herrity is thought to have perhaps twice the budget for TV and radio ads that Moore has ($200,000 versus $100,000, according to some estimates), he may be more effective than Moore at pointing the finger of blame. "Audrey's a ripe target," one Democratic Party worker said recently . . . . {Herrity} has a chance to define her and define her drawbacks."

The other theory is that Herrity's credibility is already so damaged that nothing that he says about a rival politician can stick.

Moore's media strategy is less clear. Former governor Charles S. Robb, who has endorsed Moore, taped a TV commercial for her last weekend. Her first radio ad is expected to start running today.

The Herrity-Moore debate about transportation and development, which has dominated the fall elections, has moved into the classroom. Or, perhaps more accurately, it has tried to move into the classroom.

A seminar at the Northern Virginia Center of the University of Virginia, organized by a high-ranking official of one of the area's preeminent development firms, is concentrating on the politically charged issue of transportation planning.

Most urban planners say there are two basic approaches to transportation planning: One (endorsed by Herrity) is planning and building roads; the other (endorsed by Moore) is planning and managing development so it does not clog the available road system. The seminar's syllabus mentions prominently the first approach. The second seems to have been ignored.

When Supervisor Thomas M. Davis III (R-Mason), who has sided with Moore in advocating growth controls, saw the syllabus, he called the university to see if he could address the class on using controls on growth as a tool in transportation planning. No go. Davis was told the class was filled.

Davis said he sees the hand of the development industry, which is ardently supporting Herrity's reelection, in the seminar. The organizer of the seminar is E.M. Risse, a senior vice president at Hazel/Peterson Cos. Risse maintains that government is responsible for area transportation problems. William Lucy, a professor at the U-Va. School of Architecture who is teaching part of the course, defended Risse's academic credentials and noted that several well-known transportation planners are participating in the seminar. But this, Davis said, is "really approaching the problem from one point of view."