At age 41, James M. Scott is hardly a political relic.

Yet the tall, soft-spoken Fairfax County supervisor is the last member of a moderate-to liberal Democratic coalition that only five years ago dominated the county's nine-member Board of Supervisors -- the suburban equivalent of a city council.

Now Scott faces possible political extinction in next Tuesday's election at the hands of a conservative Republican. The GOP's Gwendalyn Cody brands Scott's ideas as "socialistic" and says people are tired of paying for the social programs he has advocated during the eight years in office.

The theme of the close Scott-Cody race is being repeated in many of Fairfax's supervisor contests where candidates running on conservative platforms are given favorable odds in Tuesday's voting.

"Whoever wins, this will be the most conservative board ever," says a delighted Nicholas Panuzio, Republican county chairman who hopes his party can add at least one seat to its present three-member board minority.

"Conservatism certainly is fashionable," laments Supervisor Alan H. Magazine, one of Scott's fellow Democrats, who is retiring from office after two four-year terms. "Democrats are hesitant to talk about social programs."

But Democrats are not the only ones feeling the conservative heat. In the sprawling Springfield District in the county's southwest corner, moderate Republican Marie B. Travesky is under attack from a conservative independent and an antigrowth Democrat in a bitter three-way race whose outcome is highly uncertain.

Travesky's independent opponent, former GOP county chairman Jospeh D. Ragan, accuses her of backing public housing and exorbitant pay raises for county officials. Her Democratic rival, Carl Ericson, paints her as a growth advocate who has helped developers spoil the county's last rural area. Both have taken to lambasting her at candidates' joint night sessions in a manner that led one observer to compare them to Mafia hit men.

"It was appalling," said Supervisor Audrey Moore, a Democrat from neighboring Annandale District, who recently shared a platform with the three candidates.

Some strategists believe the attack style of campaigning has become smart politics in Fairfax County.

"The only way to beat an incumbent is to go after him," says one local Repulbican official. "Anybody who doesn't try is just wasting their filing fee."

Others think it could backfire and result in Travesky's reelection. And still others believe many politicans may have overestimated the conservative mood of the voters.

Fairfax County's election returns may prove a good test of that thesis. People take elections seriously in the 410-square-mile county of 600,000 people -- by far Virgina's largest local jurisdiction.

County Electoral Board secretary M. C. Rappleyea predicts a turnout Tuesday of between 45 and 50 percent of the county's 245,340 registered voters -- not bad for an off-off-year election when the highest office up for grabs is state senator.

"They are a sophisticated type of voter," says Joseph Wisniewski, head of precinct operations for the county Democratic party. "They're largely government affiliated -- either directly as employes or indirectly in private businesses that are government-related -- and they're more aware of and more oriented to government."

Some supervisors' candidates try to eschew party and philosophical labels.

"There is no liberal or conservative approach when it comes to neighborhood problems," says GOP contender Thomas M. Davis III, running against Democrat Betsy W. Hinkle for the vacant Mason District seat.

"What's partisan about sideyard requirements or building setbacks?" asks Travesky, who says those are the kinds of issues the board most frequently deals with.

As the area's most visible and accessible officials, they are asked to take stands on numerous growth and transportation issues.

Growth is a frequent political issue in a county that authorizes more building permits monthly than any other locality in the Washington area. One of the most popular local Democrats is Supervisor Moore, a gadfly who often finds herself on the short end of board votes but whose criticism of both growth and county spending give her an edge at election time.

Transportation is another durable issue in a county whose outmoded state-maintained roads system is choked with cars every rush hour. Even conservatives such as Ragan, Cody and Board Chairman John F. Herrity, a Republican, -- like their Republican-supported Arlington counterparts Walter L. Frankland and Dorothy T. Grotos -- have expressed full support for completion of the Metrorail system.

"They all put thier fingers to the wind and all of sudden became fans of Metro," says Magazine -- a charge Herrity and other Republicans deny.

Magazine, Mount Vernon District Supervisor Warren I. Cikins (D) and Dranesville Supervisor John P. Shacochis (R) are all vacating their seats, each of which is the subject of hotly contested races.

Perhaps the closest of the three is the contest in Dranesville between Republican Nancy K. Falck and Democrat Maya A. Huber, a maverick who shares many of Moore's reservations about the county's development. Their race has generated the most campaign contributions of any single-district contest, with Falck reporting $15,164 in contributions and Huber $11,886.

Herrity and his Democratic opponent, Vivian E. Watts, have each collected more than $26,000 in their race for the at-large board chairman's post. Most of the other candidates have reported gifts and expenditures of less than $10,000 in reports filed with the county electoral board earlier this week.