Supervisor James M. Scott is a soft-spoken Fairfax County Democrat whose advocacy of causes such as African relief, public housing for the poor and limiting American investments in South Africa occasionally have placed him at odds with the Republican majority on the county Board of Supervisors.

Democrats say that makes the 46-year-old Scott, a consultant and community college teacher, the most likely target of Republican supervisors who will decide sometime next year how to redraw the board's eight political districts.

"It's an attempt to increase Republican domination of the board," said Board Vice Chairman Martha V. Pennino, a Democrat. "And the Republicans feel that by redrawing Jim's district in certain ways, it makes him more vulnerable."

County Republicans say they have not targeted Scott, but say that Scott, a four-term supervisor who has never won with more than 53 percent of the vote, is the most vulnerable Democrat on the county board.

"We are not known for political redistricting in Fairfax County," said Supervisor Nancy K. Falck, a Republican whose Dranesville District in northern Fairfax is unlikely to experience major shifts in redistricting. "I think the Democrats' fears aren't justified."

Democrats and some Republicans say, however, that the GOP supervisors, who for the first time in more than a century gained a majority on the nine-member board last year, are certain to try to rearrange Scott's sprawling Providence District in hopes of adding a sixth GOP member to the board in the 1987 elections.

Although the board redrew the magisterial districts of its supervisors four years ago, a surge in population in the county's developing western half has left wide gaps between the numbers of residents represented by supervisors in the east and those in the west.

By law, Fairfax is required to redistrict only after the U.S. Census, every 10 years, but the board also is empowered to use state population estimates to redraw district lines every five years.

Scott's Providence District stretches between Seven Corners near the Arlington County line and Stringfellow Road in the far west of the county, encompassing Tysons Corner as well as the newer Fair Oaks Mall west of Fairfax City. In the precinct swapping and creative map drawing that accompanies redistricting in the county, politicians say, there is plenty of room for lopping off areas thought to be friendly to Scott and adding GOP strongholds to his district.

Republican supervisors say redistricting is meant to ensure the principle of one-man, one-vote by evening the population of the county's eight magisterial districts, each of which ideally would would have about 83,000 people.

Supervisor Thomas M. Davis III (R-Mason), whose district in eastern Fairfax is certain to grow, also sought to play down the Democratic concerns. "This is not a hardball political atmosphere," he said. "If you're talking about wiping somebody out . . . . You're not going to see anything major like that."

Davis and other Republicans stressed that first-term GOP Supervisor T. Farrell Egge of Mount Vernon also is considered vulnerable, having won less than 50 percent of the vote in a three-way race in his district last year. Democrats agree that Egge is vulnerable, but say they think the GOP will try to buttress his district with friendly Republican precincts when the new lines are drawn.

Democrats, including Scott, nonetheless remain suspicious of Republican intentions. They note that Scott's outspoken advocacy of public housing has drawn fire from Board Chairman John F. Herrity, a Republican.

Scott's activism on international social issues has troubled some Republicans, who contend that board members have no business meddling in affairs abroad. Earlier this year, he demonstrated outside the South African Embassy in Washington and proposed that the county sell its pension fund investments in American firms operating in South Africa that have refused to adhere to a set of guidelines advocating better treatment of blacks and other minorities.

"There are some things I feel strongly about and human rights is one of them," Scott said in an interview this week. "Affordable housing is another."

Scott said redistricting is disruptive and "is very bad for the county in trying to develop a sense of community." Other board members, Democrats and Republicans alike, agreed with that assessment.

It is unclear when redistricting -- a process that can take months -- will get under way. The county's last redistricting in 1981 was marked by secret meetings, shuttle diplomacy between supervisors' offices and precinct trading.

After the board was held by a circuit court judge to have violated the Virginia open meeting law by that process, few politicians were eager for an encore.

Nonetheless, Herrity has said the board will go ahead with redistricting in 1986, and Republicans say privately they are unlikely to spurn the chance for political advantage.