In early 1956, Fairfax County Republicans could hardly find people to run for the Virginia House of Delegates.

"Right now we've only got three for six slots," Vincent Callahan, then-candidate for leiutenant governor told high school social studies teacher James Dillard. "Why don't you run, Jim?"

Dillard thought a minute. "Hell," he said, "OK. I'll lrun."

Dillard won in that primary, but lost the general election as the Democrats swept all 13 Northern Virginia seats. As Democrats had dominated both houses of the General Assembly for more than a century, so did they dominate what is now the 51st District, the southwest portion of Fairfax County.

But today, Dillard is running for his fifth term as delegate, and to his displeasure he is running hard to retain his party's nomination. Seven Republicans are running for three seats in the 51st District --- three incumbents, a former delegate, a former primary winner and two newcomers.

This year, the Democrats won't be having a primary: They have fielded only three candidates, all newcomers, for the three seats.

The Republican candidates are Robert Thoburn, Larry Pratt, John Adams, Joe Morrissey, Robert Brostrom, Robert Harris and Dillard. The Democratic candidates are Vivian Watts, Michael Hershman and V.. Strang Jr.

"The Democrats will get slowly eaten up," Democratic political consultant Paul Goldman said in January of Virginia politcs. "They're looking at political erosion."

The change is partly the result of explosive growth in Virginia's increasingly conservative subrubs, which have become an electoral bedrock of Republicanism in the state. Nowhere is this growth more apparent than in the 51st, which emcompasses Annandale, Springfield, Bruke, Chantilly and Clifton.

All of the Republicans candidates call themselves conservatives, favoring limited government, fiscal conservation and crackdowns on crime. They reflect different shades of conservatism, but their political ideology fmay have little impact on the election.

"In an election like that in the 51st District," said Will Holder, who was Northern Virginia field organizer for the state Republican committee before leaving two weeks ago to work in Dallas for Rep. James Collins, "five out of ten people vote on name recognition. Four out of ten vote on the image the candidate protrays to them, like whether he's a family man or a religious man or whatever. One out of ten takes a strick position on one the issues and looks for a cadidate that has that position."

Both Pratt and Thoburn could draw support from those who feel strongly about a single issue, and they could be helped by a low voter turn out on Sept. 8. Pratt, a one-term incumbent, was featured cradling a shotgun in an article in August issue of Life Magazine titled the "Young Turks of the Radical Right."

He works for the Gun Owners of America Political Action Committee, which last year gave $180,000 to 54 federal political candidates, 43 of whom won. Pratt favors tougher penalties for violenta crimes and a state constitutional amendment to give citizens the right to initiate and repeal laws by referendum.

Thoburn is the headmaster and owner of the Fairfax Christian School. He served one term in the House and then lost in 1979. A portion of his support comes from opponents of legal abortion, which Thoburn strongly opposes. He said his concersn include traffic congestion, road improvement and the return of a greater share of state revenues to Northern Virginia.

Adams, owner of a paint and wallpaper store, ran on a ticket with Pratt and Thoburn in 1977. Dubbed the Three Musketeers, they are credited with Dillard's upset defeat in that year's primary. Adams later lost in the general election. This time, Adams said, he has campaigned primarily through ads in the local direct mail publication, Buyers Guide.

"I'm an issue-oriented candidate," favoring a human life amendment and elimination of sales tax on food and medicine, he said. Morrissey, 23, a third year law student, has run a high-profile camgaign, going door-to-door to almost 8,000 homes with his stands against state-funded abortion an the ERA, and in favor of the creation of a separate highway district for northern Virginia.

Brostrom, 30, is an assistant engineer for Chespeake & Potomac Telephone Co. and first-time candidate. He said is main issue is his support for the repeal of the state tax on food.

Harris is a four-term conservative who, like Dillard, favors passage of the ERA. "In this high frowth district," Harris said, "with newer families, more people are out battling for roads and worried where thier kids are going to go to school. Those issues, along with crime, are really the gut issues.

Dillard served three terms before losing in 1977 to the Three Musketeers, and then winning a seat back in 1979. Detractors charge that Dillard, who favors ERA and last year voted with Gov. John N. Dalton against the repeal of the food tax, is too liberal to be a Republican.

"That's asinine," said Dillard. "The kind of thinking voters we have in the district favor a multi-issue candidate such as myself."