Fairfax Supervisor Audrey Moore plans to think about it during her August vacation in Vermont. Supervisor Martha Pennino says she has "certainly given it more thought than in the past." And everyone says that Supervisor Tom Davis must be thinking about it -- except Davis himself.

The object of these politicians' desires is the Fairfax County Board chairmanship, the greatest political prize in a suburban locality with more people than Alaska, Wyoming, Vermont or Delaware.

For the past several months, the county's political equilibrium has been upset. Public opinion has shifted perceptibly against rapid growth and the traffic that accompanies it.

John F. Herrity, the incumbent Republican chairman who is identified with the county's development policies, was charged last week with violating the state's public disclosure law.

He is scheduled to stand trial on the charge Aug. 21 in Fairfax District Court.

There is no provision for removing him from office even if he is convicted, and many politicians assume Herrity will fight to stay in office regardless of the trial's outcome.

Nonetheless, Herrity, who just four months ago was regarded as nearly unbeatable, is now seen as the Democrats' No. 1 target in the November 1987 elections.

"I find a lot more people convinced today than they were some months ago that Jack can be beaten," said Harris N. Miller, chairman of the county's Democratic committee.

Said Democrat Moore: "I have been asked to run by a number of people. I'm thinking about it, but I don't know how seriously . . . . I'm thinking more and more that there's going to be a change" in the electorate's mood.

The coveted board chairmanship, which will pay $35,000 a year starting in 1988, is primarily ceremonial; the chairman casts just one vote on the County Board and has no executive powers. Nonetheless, as the county has grown, the chairmanship has evolved into a demanding, full-time job.

Moore, 57, who is more popular with her Annandale District constituents than she is with Democratic Party officials, would probably be forced to run a populist campaign relying more heavily on direct appeals to voters than on party organization or deep-pocketed contributors. That kind of campaign would be a formidable challenge in a 399-square-mile county with nearly 700,000 people, politicians agree.

Another Democrat thought to be weighing a race for chairman is Pennino, the board vice chairman, nicknamed "Mother Fairfax," who has served as supervisor from Centreville since 1968.

Although she is more acceptable to Democratic regulars in the county and less strident than Moore, Pennino, 68, is believed to be unlikely to mount a direct challenge to Herrity, whom she likes. Nonetheless, she said she's not ruling it out.

"Any politician who says they've never given any thought to higher office is lying," she said.

Pennino said she would not take part in a Democratic primary, however, and would accept the party nomination only if it were uncontested.

Another possible Democratic candidate who seems to have been emboldened by Herrity's difficulties and the county's political climate is Don Beyer, president of Don Beyer Volvo in Falls Church, one of the largest Volvo dealerships in the East.

Beyer, a boyish looking 36-year-old who was Gov. Gerald L. Baliles' top campaign aide in Northern Virginia last year, has been touted for months as an attractive candidate for the job by Democratic Party leaders.

Although he says he has made no decision on whether to run, Beyer does little to disguise his interest in the political maneuvering under way.

"This is a very politically propitious time," he said. "I'm trying to be discreet here . . . . I don't want to be in a position of simply capitalizing on Herrity's misfortune."

Democrats say that if Herrity is convicted of the conflict-of-interest charge, which is a misdemeanor, many other lesser-known candidates could emerge during the fall and winter to sound out their chances for the Democratic nomination.

On the GOP side, Davis, the Mason District supervisor, is widely perceived as the most likely candidate to succeed Herrity if the current board chairman in unable to run again because of his legal problems.

Despite his appetite for higher office, Davis, 37, has been boxed in politically by more senior Republican officeholders. With Herrity as chairman and Rep. Frank Wolf as the 10th District member of Congress, the usual avenues of political advancement have been closed to him.

If Herrity's star fades, politicians agree, an opening could be created for Davis.

Asked about the situation, Davis shifts and balks, clearly uncomfortable with the question.

"I just don't want to get into it," he said. "I'm not asking anybody, I'm not out there, I'm just doing what I've intended to do, running for reelection in Mason District . . . . I don't really think it's appropriate at this point for me to say anything."