BACK IN THE EARLY-BYRD era of Virginia politics, there was nothing like odd-year elections to keep a machine strong, and the formula was simple: wear down the voters with elections all the time, keep state elections separate from presidential and federal elections that might draw more people than you want--and then make sure your own people show up. Today that machine is no more, but the tiny turnouts continue--and in Northern Virginia, they knocked two veteran politicians out of office.

Fairfax County Supervisor Marie Travesky, who has been a diligent force well beyond the borders of her Springfield district, was defeated in the Republican primary by Elaine McConnell, owner and founder of a school for learning-disabled children. Mrs. Travesk, who has served with distinction in various regional efforts, including the development of Metro and projects of the Metropolitan Washington Council of Governments, lost by a 128-vote margin out of an ungrand total of fewer than 4,400 votes in the entire election.

In Prince William County, voters defeated another two-term county supervisor, Donald L. White, selecting instead John E. Bonfadini, a former legislative candidate who is a professor at George Mason University. In this contest, the vote was 805 to 699. In other Northern Virginia primaries, too, the turnouts were small, many of them in single-digit percentages of the number of registered voters.

It does not necessarily follow, of course, that small turnouts produce bad or warped decisions; conceivably, these voters represent a good sample-- and even if they don't, that's democracy and they came to do their part. Still, so long as Virginia insists on separating these contests from others, candidates may be in for many surprises, and complacent voters will take the consequences.

In the meantime, those seeking great political messages in the returns may cite all sorts of reasons for the defeats of Mrs. Travesky and Mr. White. After all, wasn't Fairfax Supervisors Chairman Jack Herrity a constant critic of Mrs. Travesky who worked hard for her defeat? True, and in a Republican test of strength, Mr. Herrity has a following. But as Mrs. Travesky noted, complacency on the part of some would-be supporters of hers probably hurt.

So what about the voters' "mood" in Northern Virginia? Call it volatile, difficult to discern, too close to call or all of the above; and take two aspirin and wait for fall.