Sunday's edition of the Washington Post incorrectly stated that Republicans in Northern Virginia have fielded a full slate of candidates in this Tuesday's election. That statement should have applied only to the region's state legislative races. In addition, the article erroneous referred to Del. Robert L. Thoburn (R-Fairfax) as being from the country's 18th District. He is running for reelection in the 19th District.

Northern Virginians will choose their state legislators and local officials this Tuesday in what could be a pivotal election here for Republicans hoping to chip away at the Democratic Party's traditional majority control of the General Assembly.

Intent on duplicating the GOP's collection of statewide successes, Republicans have fielded a record number of legislative and county government candidates. In this region alone, a total of 139 persons of various political affiliations are seeking election in various political jurisdictions.

The Democrats, who hold 34 of 40 Senate seats and 78 of 100 House of Delegates seats, have dominated the legislature for years. They don't expect any sudden turnarounds, and even Republican leaders are quietly predicting only modest gains.

Northern Virginia, however, is one of several areas in the state where the GOP is going all out to increase its impact in Richmond.

One factor in the outcome here may well be the absence of national and statewide races to lure the region's more than 420,000 registered voters to the polls. Most jurisdictions predict light to moderate turnouts, but certain local races have generated added interest.

In Fairfax County, for example -- where similar contests four years ago drew a bigger turnout than the heated D.C. mayoral primary last year -- officials are forecasting a 45-50 percent voter showing because of the sheriff and county board chairman races there.

Other local campaigns, such as the tight prosecutor contests in Arlington and Alexandria and the Arlington County Board election have earned special attention. In addition, heavy Republican spending in Prince William and Loudoun counties mark an unprecedented GOP challenge for three House seats there.

Republican Gov. John N. Dalton and other GOP officials have traveled north several times to drum up support for the party's Assembly candidates.

"Dalton's campaigned more than any governor I've ever seen," said State Sen. Hunter B. Andrews (D-Hampton), who cochairs the Democrats' legislative campaign. But he doesn't think the governor's partisan efforts will do that much good, particularly with so many Democratic incumbents in the running.

"Any incumbent has an advantage, I don't care if it's a Democrat or a Republican," said Andrews. "I just don't see any way they're going to pick up the seats they want."

For the first time in the Northern Virginia region the Republicans have put together a full slate of candidates. The most optimistic politicking, however, has been reserved for House or Senate races that are without or short on incumbents.

For this reason and others the closest Assembly contest appears to be in Fairfax County between Democratic Del. Richard L. Saslaw and former Republican Del. James R. Tate. Their race for the Senate seat vacated by Omner L. Hirst, longtime Democratic dean of the area's Richmond delegation, is the only non-incumbent contest among the region's eight Senate districts.

Saslaw and Tate are both experienced campaigners. Saslaw is completing his second term in the House, and Tate was his party's unsuccessful 8th District congressional candidate in 1976. Reports filed by both candidates show Tate outspending Saslaw three to one, but the Democrat has been campaigning door-to-door since the June primary and expects to have personally contacted homes of 15,000 registered voters by election day.

Both men cite regional and county transportation problems as being their major concerns. Saslaw, however, seldom fails to mention his support for the Equal Rights Amendment -- and Tate's opposition to it -- to underscore the philosophical differences between them.

Another race attracting a lot of attention is the aggressive GOP challenge to Senate Majority Leader Adelard L. Brault (D-Fairfax), a 14-year veteran of the Assembly.

Brault, 70, is having his toughest reelection contest in years against John M. Thoburn, the 22-year-old son of the legislature's most conservative member. Aided by some of the same supporters who helped his father, Del. Robert L. Thoburn (R-Fairfax), win an Assembly seat two years ago, Thoburn has accused Brault of contributing to the taxpaying burden by supporting "big spending" in state government.

Clearly vexed by the political assault of a newcomer, Brault stands on his long legislative experience and argues that the Democratic-controlled Assembly has kept government costs to a minimum.

Brault also warns that Dalton's enthusiastic endorsement of young Thoburn is irresponsible and sure to cause some "repercussions" in the assembly next year.

Although most observers in both parties say Thoburn will have a difficult time unseating Brault, the senior legislator has raised more than $32,000 in campaign funds. Reports show him spending nearly $17,000 of it to Thoburn's $13,000, and he is holding the rest in reserve in anticipation of last-minute spending by his young opponent.

The House races in the region have been marked by more frantic campaigning as candidates strive for name recognition and an issue to elevate them among the pack of officeseekers.

With two open House seats in Alexandria, Democrats and Republicans there are given equal chances of replacing the two incumbent legislators who chose not to run this term.

In the two huge House districts that comprise Fairfax County, Falls Church and Fairfax City, the four incumbents in each of those races are given the edge to recapture their seats in the five-member districts.

Since both districts have incumbent Democrats and Republicans, the remaining challenging candidates expect to be scrambling for one open seat on election day.

A possible exception is the 18th district where several Democratic candidates have targeted one Republican incumbent, Thoburn, for special attack. Since Thoburn ran fifth out of the five House winners in the last election, they are hoping he is vulnerable to defeat.

"Anything can happen in an election if you have a small turnout," said State Sen. Wiley F. Mitchell Jr. (R-Alexandria), who is running unopposed. He speculated that the Brault-Thoburn race may well hinge on the later's benefiting from voter apathy.

"This has been an astonishing kind of election as far as I'm concerned," said Mitchell, who complained that a recent campaign event he attended with other candidates attracted only 25 citizens "and 10 of them were there as part of a class assignment."

campaign swings by Dalton and others are "of nebulous value in changing people's minds, but do motivate party workers and help to raise money," he said.

Jeff Gregson, executive director of the Republican Party in Virginia, said the GOP organization is following the same "professional" approach to campaigning that has worked so well in past statewide elections.

"We've encouraged the candidates to hire a staff person to help coordinate a lot of little things that fall through the cracks," he said. "And we've issued weekly news summaries on state issues and supplied research on the voting records of their opponents."

In addition, the Republican National Committee has taken a special interest in the Virginia Assembly races, distributing more than $25,000 among candidates in key contests in the state.

The campaign intensity of both parties has turned this year's General Assembly election into one of the most expensive in the state's history. Reports filed to date show that Democratic candidates have spent a total of $797,500, just slightly ahead of the $748,500 spent by their Republican opponents.

The polls will be open on Tuesday from 6 a.m. to 7 p.m.