Virginians go to the polls tomorrow to decide 11 primary elections that could help reshape the General Assembly and test the influence of Gov. James S. Gilmore III as leader of a Republican Party ravenous for a solid legislative majority.

In races turning on highly local problems such as the pace of suburban growth and broader issues of state taxes and crime control, Republicans will vote in races for five seats in the House and two spots in the state Senate. Democrats will pick nominees in four House races.

Although the field may appear small--and many experts believe turnout will be low in the summer vacation season--every single contest is important to both major parties, hair-split as they are in the two chambers of the legislature.

With a razor-thin Republican majority in the Senate and virtual parity in the House, Gilmore has laid some stature on the line by choosing sides in four of the GOP races, two in Northern Virginia. The state's governors usually stay out of party primaries, and Gilmore's involvement speaks volumes about the importance to him of capturing the legislature in November's general election.

In the Washington suburbs, home to six of the 11 primaries, Gilmore endorsed G.E. Buck Waters, of Nokesville, over antiabortion activist Robert S. FitzSimmonds III, of Manassas, in the challenge against Charles J. Colgan (D-Prince William), a senator for 24 years. The governor also came out for Del. Richard H. Black, of Sterling, against David G. McWatters, a Loudoun County supervisor also from Sterling.

Other area races include a Democratic House primary between Billy Gray Tatum, of Haymarket, and Denise M. Oppenhagen, of Woodbridge, for the right to challenge Robert G. Marshall (R-Prince William), a delegate for eight years; a Democratic race in McLean between Carole L. Herrick and John W. Foust, both vying for a shot at Del. Vincent F. Callahan Jr. (R-Fairfax), who has been in the assembly 32 years; and a Democratic race between G. Gary Jacobsen and Virginia M. Stephens, both of Woodbridge.

Stephens and Jacobsen want to challenge Del. Michele B. McQuigg (R-Prince William), who was elected last year to fill the vacancy created when David G. Brickley (D) was enticed to join the Gilmore administration. Stephens had worked in earlier Brickley election efforts.

In the Senate district that includes part of Fauquier County, Republicans are battling as incumbent H. Russell Potts Jr., of Winchester, defends his seat against P.M. "Mike" McHugh, of Front Royal.

Polls open at 6 a.m. and close at 7 p.m. Virginia does not register voters by affiliation, so there may be some crossovers as local party organizations try to influence their rivals' outcome. Some primaries for county offices are on the ballot in Prince William, Stafford and Fauquier.

Gilmore, whose chief of staff, M. Boyd Marcus Jr., is a savvy veteran of GOP politics in Virginia and influenced his endorsements, has played a high-profile role in the election, backing candidates across the spectrum of a party that for years has been swept by ideological currents.

For instance, in a House Republican primary in Richmond's prosperous West End, Gilmore has endorsed a staunch conservative challenger over a moderate incumbent who repeatedly has voted against him. Similarly, in Loudoun, he endorsed Black, who is one of the most conservative delegates in Richmond.

Elsewhere, though, Gilmore has leaned more toward the middle, endorsing the more moderate Waters in Prince William and a centrist in a Culpeper area House race who had in the past been supportive of the incumbent Democrat, who is retiring.

"The governor got into these races to win," said Press Secretary Mark A. Miner. But, he added, "this is not a referendum on the governor."

As Gilmore traveled in South America last week on a trade mission, Miner said the governor was trying to expand the party's legislative base by reaching out to a variety of candidates, not just conservative ones.

"There is no carbon-copy cutout" candidate whom Gilmore supports, Miner said.

Craig K. Bieber, executive director of the state Democratic Party, disagreed, saying Gilmore's hodgepodge of endorsements reveals how desperate he is to obtain at least a 53-seat majority in the 100-member House--which could solidify his agenda--instead of a narrower 51-seat majority that could dissolve on crucial votes.

"The governor is hedging his bets," Bieber said. "He wants to have a couple of sure winners."

Miner described tomorrow's election as the curtain-raiser on what could be a new era of Republican control in state politics, with all three statewide offices held by the GOP and the legislature firmly controlled by the party.

But although Gilmore's message of lower taxes resonated in the 1997 governor's race, what happens tomorrow may turn on issues that matter closer to home, Miner cautioned.

"What a candidate in Northern Virginia is running on is not necessarily what a candidate in Southwest Virginia is running on," Miner said.

Gail Nardi, a Democratic strategist for the fall elections, agreed. "It's all about fundamentals," she said. "It's ground warfare."

Activists in both parties say the primaries could foreshadow the November elections, when all 140 assembly seats are on the ballot. One barometer--the money being raised this season--is a likely harbinger of the extremely expensive autumn campaigns for ostensibly part-time legislative jobs that pay about $18,000 a year.

For instance, in Richmond, in the most closely watched Republican primary in the state, Del. Anne G. Rhodes and challenger Ruble A. Hord III, whom Gilmore endorsed, are together headed toward the half-million-dollar mark in spending by tomorrow, according to campaign finance reports newly filed with the state.

Rhodes has raised $93,000 in the last two months and has $16,800 on hand, her report said. Hord, who has lent himself $200,000, raised $101,924 in the same period and has $4,260 on hand, his filing said.

Most analysts say that Gilmore's prestige as a power broker will not rise or fall dramatically if he wins or loses even two or three of the four candidates he backed. The true test of his and the party's influence will come this fall, they say.

"Tuesday will mark the beginning of an historic time . . . as Republican ideas take hold," Miner said.

Bieber, of the Democrats, said Gilmore's endorsements tell his fellow Republicans that "you have to march with me in lockstep, 100 percent."

"By doing what he's doing, he's helping us," Bieber said. "It raises the question: Can we trust this guy as he remakes state government in his image?"

Staff writer Craig Timberg contributed to this report.

Northern Virginia Primaries

Democratic Primaries

House District 13 (Prince William)

Billy Gray Tatum

Denise M. Oppenhagen

House District 34 (Fairfax)

John W. Foust

Carole L. Herrick

House District 51 (Prince William)

G. Gary Jacobsen

Virginia M. Stephens

Prince William: Clerk of Court

Joyce M. Sowards

Louis Ginesi Dominguez

Republican Primaries

House District 32 (Loudoun/Fairfax)

Richard H. Black

David G. McWatters

Senate District 27 (Fauquier)

H. Russell Potts Jr.

P. H. "Mike" McHugh

Senate District 29 (Prince William)

G.E. Buck Waters

Robert S. FitzSimmonds III

Prince William: Gainesville Supervisor

Martha W. Hendley

Kevin Paul Childers

Edgar S. Wilbourn III

Fauquier County: Clerk of Court

John Marshall Cheatwood

Gail H. Barb

Fauquier County: Lee District Supervisor

S.L. "Serf" Guerra

Sharon Grove McCamy

Fauquier County: Cedar Run District Supervisor

J. Mark Rohrbaugh Jr.

Raymond E. Graham

Stafford County: Commissioner of Revenue

Kenneth Mitchell

Scott Mayausky

Stafford County: Sheriff

Charles Jett

G.W. "Jerry" Tolson