Besides drumming up support for presidential and congressional candidates or scrapping for political power within their parties, Northern Virginia Democrats and Republicans have something else in common: a good case of convention fever.

For Democrats, the convention uppermost in their minds at the moment is the state party meeting May 16 and 17 in Richmond. In addition to selecting 14 at-large delegates to the national convention this summer, the Democrats will focus on the critical task of picking state party leaders to guide the Democrats' state and national campaigns this fall.

Three weeks after the Democarts move out, Republicans will hold their convention in Richmond -- June 6 and 7 -- and will grapple with similar issues.

Northern Virginia Republicans will barely have concluded the state get-together before they face a spirited GOP primary in their two congressional districts -- the 8th and the 10th -- on June 10.

A glimpse of the skirmishing in both parties that is likely to occur between now and the two national conventions this summer was provided last weekend at separate meetings of area Democrats and Republicans.

Democrats from the 8th Congressional District spent last Saturday at a Fairfax County high school, laboriously choosing five national convention delegates and the district's representatives to the State Central Committee.

At another high school, Fairfax County Republicans efficiently named three national convention delegates, and then, with more of a brouhaha, dumped their county party chariman in favor of a more conservative leader.

Somewhere in all this there is talk of Carter, Kennedy, Reagan, Bush and Anderson, but the fundamental struggle has focused more on party ideologies than on Virginia's presidential choices.

"We've got to maximize our strength," said attorney George C. Rawlings Jr., chairman of a group of liberal Democrats who hope to stop what Rawlings calls "the headlong dash to give our party a conservative image."

Although Rawlings practices law in Fredericksburg, he lives in Gunston, just south of Mount Vernon, and thus was one of 300 Democrats at the 8th District meeting to play tug-of-war over party philosophies.

By day's end, he and four other Kennedy supporters had been named to fill five of the district's 15 seats on the State Central Committee. Considering that nearly all of Kennedy's delegate strength in the state has come from Northern Virginia, the liberal showing was not unexpected.

Rawlings has been a member of the Democratic National Committee since the liberal wing won control of the party at the 1972 state convention. However, he can expect a rougher time of it this year if he tries to hold onto the national post. So far, Carter has a seven-to-one lead over Kennedy in party contests for Virginia's 64 national convention delegates (currently, Carter has 35 Virginia delegates and Kennedy has five), and that is bound to bring some changes in state party leadership.

Bob Reveles, Kennedy's 8th District coordinator, thinks otherwise. He is convinced Carter's support is slipping among Virginia's Democrats, and he hopes the president's losses will be Kennedy's gains.

"The commitment to Carter is not very deep," Reveles contends. "We're hoping to hold what we have and be able to be there when events start turning against him."

Reveles theorizes that continued economic and international turmoil could mean "an open convention" in New York this August.

As for Rawlings, Reveles hopes that both Carter and Kennedy backers will decide that the state party "needs that kind of opinion and infusion of new ideas."

Fairfax County Democratic activist Emilie Miller cautions that Kennedy supporters should not count on any defections from the Carter camp. Miller, former party chairman in Fairfax and a Carter supporter, concedes that there is not the same kind of enthusiasm for candidates there was four years ago. The emphasis now, she says, is on party control.

"I consider myself a liberal," says Miller, although she criticizes Rawlings' brand of liberalism as "exclusionary" and laments the fierce ideological in-fighting she said is going on in both parties.

"Here's the Republicans doing everything they can to go to the right and the Kennedy supporters doing everything they can to go to the left -- what happens to us in the middle?" she asks. "And where are the Bush and Anderson people going to go?"

Some Northern Virginia Republicans have been asking the same questions. Saturday's Fairfax GOP meeting suggested to some Republicans that they have no place in the party "unless we pass the litmus test," as one angry party member put it.

People who classify themselves as moderate or even conservative Republicans were stunned when the county party chairman Nick Panuzio, a Reagan supporter, was outsted by the even more conservative William Olson.

"Nick was just not 'right' enough for tehm," groused an aide to one Republican congressional candidate.

And Dottie Schick, Olson's counterpart in the Fairfax Democratic committee, says she hears from Republican friends that it is getting to the point that "if you want to run for office as a Republican, you have to be a right-to-lifer."

Certainly, the debate over abortion has attracted a great deal of conservative involvement in Northern Virginia politics of late. The abortion question and other one-issue controversies are sure to surface in the upcoming primary battles in the 8th and 10th congressional districts.

Although Olson says he plans to find a neutral corner in both primary contests and wants to concentrate only on "building the party," it is no secret that most of his supporters expect to back the more conservative congressional candidates.

That is expected to help ultraconservative Robert Thoburn in his bid against Stanford Parris for the right to challenge the incumbent in the 8th District, Democrat Herbert E. Harris.

The 10th District GOP primary contest -- between Frank Wolf, Fairfax Del. Martin Perper and Falls Church Mayor Harold Miller -- is not expected to set off the same kind of philosophical split, particularly since Wolf was the party's choice two years ago to challenge the incumbent, Democrat Joseph L. Fisher.

But Gene Cantrell, who is Parris' campaign manager, and Perper are counting on the Panuzio upset to attract a lot of "regular Republicans" to the polls in the primary.

"Very obviously, there's a power struggle going on in the party," says Cantrell. "i don't think Olson's election will have all that much impact on the congressional race . . . but it sure got the attention of county Republicans."