Northern Virginia Republicans said yesterday that the results of Tuseday's primaries presage a strong GOP showing in the region's November elections.

In Fairfax County, especially, Republicans boasted of their increased voting strength, noting that for the first time in the history of the huge political jurisdiction Republicans had outvoted Democrats in a primary.

"This is the higest turnout we've ever had in a Republican primary," said Del. Vincent F. Callahan Jr. (R-Fairfax), one of the many incumbent officeholders who won their party's renomination Tuseday.

Fairfax County Republicans outvoted Democrats by less than 200 votes, but even that slight margin was striking when compared to past primary results.

Four years ago, according to Mel Rappelyea, the county's election board secretary, only 8 percent of all registered voters cast Republican ballots compared to an 11 percent primary turnout for the Democrats.

This time, Rappelyea said, the Democrats and Republicans ran about even in voter turnout, with the Democrats having one of their lowest primary showings in memory. He attributed the lethargic turnout, in part, to the absence of any bond issues on the ballot.

"We always know there's a low turnout in the primary, but this was even lower than in 1975," said Emilie Miller, who chairs the Fairfax County Democratic Committee.

Miller blamed "a lot of apathy" as the reason more Democrats did not go to the polls, but she predicted voter interest would increase considerably in November.

The primary races of both parties included a couple of contests that became bitter as the voting neared. But there were few primary surprises.

State Sen. Charles L. Waddell (D-Loudoun) easily fended off a determined challenge by Del. Raymond E. Vickery Jr. (D-Fairfax) by getting the election help he needed and expected from his Loudoun County home base.

Miller said Vickery had been "very gracious" in defeat, and she noted that he, Waddell and the other winners and losers in the Tuseday primary would be meeting tonight to discuss full election strategies.

"I think there was a lot more emotionalism in the Republican races, a lot more ideological splits," Miller said.

Callahan conceded the very divergent ideological differences between conservative, moderate and liberal Republican candidates, but he said "it's nothing new." The party's conservative wing "did a good job" of nominating newcomer John Thoburn over former commowealth secretary Cynthia Newman for a State Senate seat, Callahan said.

Thoburn, the conservative son of conservative Del. Robert Thoburn (R-Fairfax), who also won renomination, will challenge Sen. Adelard L. Brault in November. He won the nomination over Newman by slightly more than 300 votes in very light primary voting.

Conservative interest groups such as those that backed Thoburn "tend to get swallowed up in the general [election] when more voters turn out," said Callahan.

In addition to the Deomcratic and Republican nominees, three candidates have filed as Independents in the general. They are former Fairfax County GOP chairman Joseph Ragan Jr., who will be running for a county board seat from Springfield; James Settie Jr., who is running for county sheriff, and Lea Anderegg, who is running for a House seat from southern Fairfax. CAPTION: Chart, Northern Virginia Primary Election Results