Following the Democratic election triumphs in Virginia this month, some GOP strategists are saying that Republican incumbents around the state are taking no challenge from the Democrats lightly, even in solidly Republican Fairfax County.

So it was with some trepidation that aides to Rep. Stan Parris reacted to an advertisement that appeared in several recent issues of The Washington Post. Could the ad -- which declared in block letters, "It's not too late, Herb." -- presage a fourth congressional race between Republican Parris and former Democratic congressman Herbert E. Harris II in the 8th Congressional District?

Parris aides hoped not. The three races have been marked by bitter partisan attacks and vivid polemics.

Harris defeated incumbent Parris in the post-Watergate Democratic tide of 1974. He served three terms representing the district, which includes Alexandria, southern Fairfax County and parts of Prince William and Stafford counties. Parris rallied to oust Harris in 1980. In their rubber match in 1982 -- the first $1 million congressional campaign in Virginia history -- Parris managed to hang on to his job by 2 percent of the vote.

The Post advertisement prompted more than 20 telephone calls to Parris' Washington office "from Republican activists who have for years maintained a Herb alert," said a Parris spokesman.

The Harris-Parris races were so hard fought, the aide said, that "a lot of our supporters bear memories and scars, and whoever placed this ad touched a nerve among the Republican faithful, who are feeling a little gun-shy these days." He was referring to the results of this month's elections in which Democrats swept the top three statewide offices and strengthened their overwhelming majority in the Virginia House of Delegates.

As it turns out, Parris has no cause for worry -- not from Harris, at least. The ads, according to the advertising department of The Post, have run in papers around the country as part of a "teaser" promotional campaign and are not connected with the former congressman. Just what is being promoted is still under wraps, but it should be unveiled soon.

Harris, for his part, says he is not planning another run for Congress. He is a principal in the Washington law firm of Harris & Berg, working in international trade law and lobbying.

He said he reacted with "mild curiousity" to the ad but quickly concluded that "there's more than one Herb in the land."

Harris and Parris almost never see each other, the Parris aide said, and they do not share "a particularly close relationship."