IF YOU NEED an example of real down-and-dirty "negative campaigning," one which would not be touched by the proposed congressional cleanup and which helps illustrate why such a law would be pointless as well as clumsily intrusive, cast your eye only as far as Northern Virginia. In Fairfax County, the campaign air is thick with flying mud -- yet armchair analysts are concluding that moderation is reigning on the rocky road to election day in November. Tuesday's party primaries may in fact may be "secondaries" by the time the voters muster again more than four months from now. Nevertheless, the Republicans and Democrats have more or less sorted themselves out for the battle, with each party pointing to the latest results as indicators of good things to come. It looks like an ugly time ahead too.

Those Republicans who call themselves "moderates" are cheered by the GOP primary victories, which went to their kind of candidates. Democrats, on the other hand, are seizing upon the closeness of some of the Republican victories as evidence that the GOP is in deep trouble come November.

There's been nothing moderate about the campaigning though. Some samples of the sweet tone of debate so far:

An anonymous obscene letter mailed this past week to supporters of Democrat Audrey Moore's campaign to unseat board of supervisors chairman John F. Herrity is the latest in a rush of scurrilous election literature. The letter, purported to be addressed to Mrs. Moore from Mr. Herrity, has been roundly denounced by Mr. Herrity, who along with Mrs. Moore has asked for an investigation.

A Republican candidate for the state senate, Gerald A. Fill, says he was the target of literature accusing him of attacking an umpire at a Fort Hunt Youth Athletic Association baseball game last summer. Mr. Fill says he did argue with an umpire but never struck the official; Mr. Fill's primary opponent -- who defeated him by a less-than-200-vote margin, denies any connection with the letter.

Republican County Supervisor Nancy K. Falck says she was accused unfairly by her unsuccessful primary opponent, Lloyd Thoburn, of using zoning laws to discriminate against conservative churches. The charge was contained in a pamphlet distributed in churches, she says. Mr. Thoburn has defended the material, saying it's a fair criticism.

The Democratic nominee who will face Mrs. Falck -- Lilla Richards -- accuses Mrs. Falck of trying to manipulate the primaries. Mrs. Richards claims that the candidacy of Franklin S. Holland Jr. -- whom she defeated in the Democratic primary -- was a ploy by the Falck camp to prevent Democrats from crossing over to the GOP primary to vote against Mrs. Falck.

If you are still with us, there's yet another ball of campaign wax. Democratic officials are saying that the last-minute entry Tuesday of Robert Thoburn -- father of Lloyd Thoburn -- as an independent in the Nov. 3 election will split the GOP vote and increase the chances of Mrs. Richards.

Meanwhile, many of the same analysts who see moderation also see in Mrs. Falck's narrow victory a message from voters that there is a big backlash against development and that incumbents of all kinds may be in serious trouble. Will incumbents now try to outdo each other as friends of enemies of development? Or will everybody scramble for the center as advocates of "controlled development," with freedom, justice and better roads for all?

Whatever roads may be in store for the voters, at this point a high one is sorely needed.