The largest contributor to the Virginia gubernatorial campaign this year was not a labor boss or utility executive, but Jim O'Quinn, a shy, naive, country boy who sells Fords to his neighbors in this Southwest Virginia mountain hamlet.

O'Quinn gave $25,000 in cash and more than $8,000 worth of in-kind contributions, including the use of his luxury automobiles, to Democratic Gov.-elect Charles S. Robb. The total contribution of $33,000 was a larger gift than any from local coal barons to whom O'Quinn sells white Continentals and more even than that given by Lady Bird Johnson, Robb's wealthy mother-in-law.

Besieged by questions about why he donated $33,000 -- only $100 of which is tax deductible -- O'Quinn said simply: "I believe in Chuck. It was my chance for a part of history. I'm not fanatical about it, but I think Chuck is destined to be president."

O'Quinn said that he wants nothing from Robb but the satisfaction of having helped.

"The press might not understand," he said. "I'm a hillbilly. I'm comfortable with what I did. The reasons are within myself."

Coming from any of the usual big contributors, whose charity can be traced to their various special interests, that might sound unconvincing. But to those who know O'Quinn, such as Joe Smiddy, chancellor of Clinch Valley College in nearby Wise, the explanation makes perfect sense.

"He's the absolute, most humble fellow," said Smiddy, who long has been active in local Democratic politics. "He told me that he didn't want anything. He just decided Chuck was for real. Jim's unique in American politics, especially when everybody's out to get something."

O'Quinn, 4l, first met Robb in the spring of 1977, when Robb came here to the hollows of Dickenson County seeking support as the untested candidate for lieutenant governor. O'Quinn invited Robb to stay with him at his modest home in this town of 400 any time he was here. There are few motels in this part of Virginia, and O'Quinn was "really thrilled" when Robb called about a month later to take him up on the offer.

"We hit it off," said O'Quinn of the bond that quickly formed between the celebrity city lawyer and the country car salesman.

"Jim's quite a guy," said Robb. "And I really don't think he is looking for anything in return."

Like many political groupies, O'Quinn loved the campaign -- and his supporting role just out of the limelight. Although as a member of the Primitive Baptist Church he does not drink, dance, curse or tell off-color stories, O'Quinn showed up at cocktail parties and fund-raising dinners all over the state and picked up the tab for a country club dinner featuring Lady Bird Johnson. His role during the campaign most often was to stand in a corner, chain-smoke Barclay cigarettes, and grab for the check whenever anyone would let him.

O'Quinn, the fourth of 10 children of a coal miner, worked as a shoeshine boy on a sidewalk here. By 10th grade, he was working at the Chevrolet garage. By 1970, with a high school degree and money borrowed from the soon-to-retire owner of the Chevy garage, O'Quinn opened his Ford dealership. The regional Ford representatives told him he could expect to sell 75 cars a year. O'Quinn sold nearly that many in a month from a corner lot without a showroom, and with a trailer for an office.

Until the chance meeting with Robb, the closest association O'Quinn had had with politics was when his father was elected clerk of Dickenson County in 1960. O'Quinn was embittered by that experience when the voters turned out his father four years later. O'Quinn's only previous campaign contributions had been $500 to Robb in 1977 and $3,000 to Robb's losing running mate for governor that year, populist Henry E. Howell.

But in May 1980, when Robb's finance chairman, Del. Alson H. Smith of Winchester, invited O'Quinn and his wife, Emma, to a fund-raising party at Robb's home in McLean, O'Quinn was quick to support Robb again.

"Al's pitch," O'Quinn remembered, "was that he wanted to raise $100,000 that night, and that he would if each of us gave $1,000." O'Quinn did, and that was the beginning.

Not one of the millionaires who dot the hills here, O'Quinn said that his annual income is less than $100,000. He was able to afford the contributions -- made in $1,000 and $5,000 amounts -- because they were spread over 18 months, he said.

"It just happened," said his wife, Emma, a former schoolteacher who also gave $1,000 in her own name. "It was our time of life to be interested in politics."

"I don't think I've ever met anyone like him in politics," said Robb.

To the cynical, however, the question nagged: Isn't there anything O'Quinn would take from Robb in return for O'Quinn's generosity?

"If Chuck came to me and said it was important to him for me to do something," said O'Quinn. "But I can't imagine what that would be."

Nothing else, he was asked as the campaign drew to a close? How about a spot on the state highway commission, perhaps, or the chance to sell a fleet of Ford cars or trucks to the state? Is there nothing?

"All right," O'Quinn said finally, in exasperation. "Maybe there is one thing: You know, to my knowledge, I've never seen the state Capitol, never laid eyes on it. Maybe, if Chuck wins, he'll give me a tour."

Inauguration day is Jan. 16, and Robb said that on that day -- or any day -- he will be glad to escort Jim and Emma O'Quinn through the marble halls of the Capitol.