Fairfax County Supervisor Audrey Moore, capitalizing on opposition to the rapid growth that county board Chairman John F. Herrity has embraced and Herrity's driving infractions and misdemeanor conviction, holds a strong lead entering the last month of the race for chairman of the County Board of Supervisors, a new Washington Post poll shows.

Moore, a Democrat who has represented the Annandale District in central Fairfax for 15 years, is ahead in all areas of the 399-square-mile county, according to the poll.

She leads Herrity among men and women, longtime county residents and new arrivals, and among voters of all ages, income levels and ideological persuasions. Those who consider themselves Republicans are the only identifiable group that favors Herrity, a Republican.

Countywide, Moore holds a 12-point lead among the 1,146 registered voters surveyed, with 45 percent saying they favor her, 33 percent favoring Herrity and 22 percent undecided.

Among those most likely to vote in the Nov. 3 election, Moore's support is somewhat stronger, with 48 percent for her, 34 percent for Herrity and 18 percent undecided. The survey, conducted from Sept. 14 through 22, has a margin of sampling error of plus or minus 3 percentage points.

The Post poll did not ask about two independents in the race for chairman, James S. Morris Jr. and R. Terry Robarge.

Respondents rated Moore as more effective on both the issue of growth and development, which she has stressed in her campaign, and the question of who would best manage transportation problems, an area Herrity has cited as his principal strength.

More than a third of those who said they voted previously for Herrity, who has held the county's top elected office since 1976, said they are supporting Moore this year.

Perhaps most ominous for Herrity, three out of four voters surveyed by The Post said they favor slowing the pace of growth in Fairfax, a position Moore has embraced for years.

Herrity, meanwhile, has maintained his longstanding view that growth has brought economic prosperity and first-rate public services and amenities to Fairfax.

The poll shows that Moore also enjoys somewhat more loyalty than Herrity, with 46 percent of her backers describing themselves as "strong" supporters, compared with 40 percent of Herrity's.

The survey also indicated that Herrity's biggest problems with the voters are those that may be difficult to eliminate in the five weeks remaining in the campaign: a string of traffic tickets for driving infractions, a misdemeanor conviction last year for violating a state public disclosure law and a perception that he is too close to land developers.

Janice Spector, a spokeswoman for Moore, said yesterday that the poll results are "consistent with what we've been hearing." She added: "We are of course encouraged by the results, but that's by no means going to slow us down in the next couple of weeks. The final poll is indeed on Election Day."

Tom Herrity, the chairman's son and campaign manager, said he was not surprised by the poll results. He added: "The No. 1 issue in the poll is transportation, and I don't think that people in this county are ready to vote for somebody who has consistently voted against transportation" -- a reference to Moore. "When people understand Audrey's voting record against major road projects -- I-66, the Springfield Bypass, et cetera -- we will be fine. By Election Day they will know that."

The number of survey respondents who said they are undecided is relatively low for this stage in a local election, perhaps reflecting the electorate's familiarity with both candidates as well as sharp contrasts in their philosophies, records and personal styles.

Herrity, plain-spoken and occasionally gruff, has been a champion of the county's rapid economic development since he was first elected to the board as a supervisor in 1971 and then elected at large as its chairman in 1975.

Moore, outspoken and occasionally shrill, has been a gadfly on the county board since she was first elected, also in 1971. She has consistently sought to slow the pace of growth by opposing major development projects and such public facilities as new roads, water intakes and sewers.

The prize they are seeking, the county board chairmanship, carries no executive duties and only one vote on the nine-member body. However, it offers its occupant an unparalleled platform from which to frame the county's salient issues. In January, when the chairman and board members take office, they will receive the same salary: $35,000 a year.

Herrity and Moore have defined the extremes of Fairfax politics for more than a decade as the county has grown at a rate of at least 1,000 people a month, transforming a locality once known as a residential satellite of the District into an employment center with many of the problems and advantages of a large city.

Today, with a population of more than 710,000, Fairfax has more people than do five states and about the same number as San Francisco, the nation's 13th largest city.

The Post survey was conducted just as the first of Herrity's television advertisements went on the air. Other TV ads, as well as radio spots, are scheduled for the coming weeks as Herrity presses a significant fund-raising advantage over Moore. Herrity campaign strategists say they are hopeful that an October media blitz will overcome Moore's lead.

Moore also is planning radio and television advertising, including a television ad featuring former governor Charles S. Robb, who has endorsed her.

Robb, a Democrat who commands the respect of the business community, is more popular in Fairfax than any other prominent state or local official named in the Post's poll.

On the key issues of traffic and growth, Moore enjoys a clear advantage. Forty-three percent of the respondents said she would do an excellent or good job handling traffic, while 29 percent said Herrity would do as well. More than half said Herrity would do a poor or just fair job with traffic. Those questioned were also less confident of Herrity's ability to manage growth and development.

Nearly a third of Moore's supporters cited her stand on growth and development as the major reason they plan to vote for her -- the most frequently mentioned reason. Eighteen percent of Moore's supporters said they would vote for her largely because they disliked Herrity, the second most frequently mentioned reason.

In contrast, 3 percent of Herrity's supporters said they supported him because of their distaste for Moore.

Three times as many respondents said they had a favorable view of Moore. Asked the same question about Herrity, however, about the same number of respondents said they had an unfavorable impression of him as those who had a favorable view. One-quarter said they had no opinion of Herrity, and 38 percent said they had no opinion of Moore.

Herrity appeared to suffer most in the public eye from his position on growth and development, which was mentioned by 22 percent of Moore's backers as the reason they opposed him. Another 16 percent of Moore's supporters said Herrity is too close to developers and the business community. Thirteen percent of Moore's backers mentioned Herrity's legal problems and driving record, and 10 percent said he is dishonest or untruthful.

Herrity has been plagued by those perceptions at least since August 1986, when he was convicted on a misdemeanor charge of failing to disclose his business partnership with a developer before voting on the developer's land-use project. That case, coupled with his longstanding pro-business and pro-development views, appears to have fostered the impression that he is too close to developers.

The Post has also reported on a 1977 case in which Herrity, who owns an insurance business, voted for an office building project shortly after he sold the project's developers $500,000 in life insurance.

Herrity's driving record, which for a time was something of an amusement among his supporters, has turned into an embarrassment and a political liability, according to Herrity's campaign strategists and the Post poll.

The chairman has received at least seven tickets -- for speeding, running a red light, operating in violation of a restricted license and failing to control his car -- since 1985 and may be on the verge of losing his license. He has received at least 18 tickets since he became county board chairman in 1976. None of them involved alcohol.

One campaign strategist for Herrity, who asked not to be identified, said recently: "The driving tends to reinforce the image of Jack as reckless -- reckless on development and reckless behind the wheel. It's a problem for him."

Herrity's supporters generally cited his experience as the major reason they plan to vote for him. More than two of five of his backers -- 43 percent -- said they plan to vote for him because he is the more experienced candidate. Another 15 percent said they support him because of his position on growth and development.

In the view of 23 percent of Herrity's supporters, Moore's biggest drawback is her position on growth and development. The next largest group of Herrity's backers, 6 percent, said they oppose Moore because she is a Democrat. Five percent said she is dishonest or untruthful. Of the remainder, a substantial number had no opinion of Moore.

Moore's support cuts across the ideological spectrum. Among the 16 percent of respondents who describe themselves as conservatives, 60 percent support her. Among moderates, who make up 45 percent of the electorate, Moore leads 48 to 32 percent, with the remainder undecided. The 3 percent of respondents who said they are liberals favor Moore over Herrity by 68 to 14 percent. Herrity and Moore roughly split the 25 percent of respondents who said they do not think of themselves in those terms.

The results also reflected a gender gap, with Moore leading Herrity by nearly 2 to 1 among women. Men backed her by a smaller margin, 43 to 36 percent for Herrity, with 21 percent undecided.

Although Moore leads Herrity by about the same margin among longtime residents of the county and new arrivals, more of the newer residents are undecided between the two candidates. Both campaigns are expected to focus on these so-called new voters -- people who have moved to Fairfax since the 1983 elections and lack familiarity with either candidate -- in the final weeks of the race.