Nathan H. Miller, Virginia's Republican lieutenant governor candidate, had expected to be making friendly phone calls to supporters last Wednesday afternoon. Instead, Miller found himself besieged by reporters demanding he explain why he had used his legislative position to help one of his law firm's clients.

They questioned Miller's ethics and hinted that he was -- for the second time in the last two months -- caught uncomfortably close to a conflict of interest.

That his judgment would be examined so publicly during his campaign was an unexpected twist for 38-year-old Miller, a man who started out as a conservative Christian Shenandoah Valley farm boy and once saw life as a simple choice between right and wrong. But because Miller was ambitious, he decided to compete in a world where opinions of good and bad diverge, a skeptic's world where a man's motivation can't be determined, but the results of his actions are judged by all.

In Miller's case, those results -- laws that gave more than $13 million in business advantages to his law firm's electric co-op clients and an amendment that could make it easier for another client to win lucrative mineral rights -- have become the only controversial issue in all the statewide races.

Virginia's conflict of interest laws are so weak that legislators are virtually left to set their own code of behavior, and accusations of wrongdoing are increasingly common. Yet, it is Nathan Miller -- who won his Senate seat after charging his opponent with a conflict similar to an arrangement Miller himself is now involved in -- who has come to symbolize the maze of overlapping and unpoliced interests in the Virginia state legislature.

"It seems to me that my motives and mine alone are being subjected to microscopic examination on every bill I have ever introduced, regardless of its merits and regardless of its needs," a dejected Miller said.

Miller's activities on behalf of his law firm's clients have caught the publicity, but there is much more to Nathan Miller. He is a classic American story of a man with few social advantages who made it to the top through discipline, determination and moxie.

The farm boy who began the long passage to successful lawyer and politician changed along the way. But he retained the belief that no matter what others might say, his own motives are pure. And he retained his ingratiating country charm, his view that right and wrong are clear and his driving ambition to make something of himself, as his parents had urged.

He grew up on a livestock farm in the sleepy little town of Bridgewater. But he was always a competitor -- as a high school linebacker, pole vaulter and student government leader, and as a fresh-faced young delegate who defeated a veteran senator in 1975. Last summer, Miller challenged the state GOP establishment at the party convention and to the surprise of almost everyone, won the lieutenant governor nomination.

But all of this was before Nathan Miller became the symbol of how business is sometimes done in a Virginia legislature that has long refused to pass conflict-of-interest laws as tough as those found in most other states. That refusal predated Miller -- who voted against stricter conflict laws last spring -- but it has changed his odds for victory.

"Nathan thinks he's cunning, but he's not as cunning as he thinks he is," said one Miller campaign worker. "A smarter man would never get himself into this . . . I'm afraid that Nathan is only smart enough to be dangerous to himself." Other supporters say that if anyone can survive such a political test, it is Miller, who has won reelection in his largely rural district despite an undistinguished legislative record.

"Nathan would literally -- I mean literally -- beat his head against the wall for eight hours at a stretch if he thought that was what it takes to make the walls come tumbling down," said Donald D. Litten, Miller's political mentor and a senior partner in his law firm.

Miller began young adulthood as a conscientious objector. Since winning the lieutenant governor's nomination, however, he has publicly renounced that belief. His political philosophy is conservative, in contrast to his opponent, Richard J. Davis, a 60-year-old businessman who is the most liberal candidate in this year's statewide races.

Campaigning from courthouse to courthouse as Virginia hills turn crimson, the boyishly handsome Nathan (nobody calls him Mr. Miller) displays the easy, down-home style that is his greatest campaign strength. In the Southside city of Martinsville, he gets uproarious laughter from two women when he says the only thing he's ever won -- other than elections -- is a block of cattle salt at a farm bureau picnic.

And later to a funeral director who is trying to take his pulse: "I'm feeling just fine. Now don't you go looking for business, you rascal!"

Beneath the relaxed corn pone and buoyant energy, however, Miller is dead serious about his ambition: "I think if, or should I say when, I'm elected lieutenant governor, I will be perceived to be a viable candidate for governor."

Garland Miller's red-brick farmhouse hugs a hill outside the tiny town of Bridgewater, and the view from its windows outlined the boundaries of young Nathan's world: the fields that Garland and his brothers worked, the barn and the turkey coops where Nathan fed livestock, milked cows and swept stalls, and the winding Rte. 42, which leads to the Church of the Brethren where his family has worshipped for generations.

Farm work was arduous, but young Nathan preferred the brisk scent of the valley air to schoolwork under the watchful eye of his mother. Edith Miller expected her three children to be the best, and when they didn't perform as well as her instincts told her they could, her disappointment was obvious. "She was strict -- not in the sense she mandated things, but in the sense she expected things," said Miller.

As a girl, Edith Miller had been forbidden by her minister-father to play cards or dance, and her religious faith was strong. The message was not lost on Nathan, who lived in his parents' farmhouse until he was past 30. It was years before he could accept people who smoked, swore or drank liquor. "I grew up thinking that there were right and wrong answers to almost everything," he said.

By high school, Nathan showed the charm that was to characterize his political style: With a smile, a gesture, a friendly look, Nathan Miller put people at ease. "He wasn't the most flamboyant guy in the class, but you knew you could always depend on him," said Larry Bowers, a Harrisonburg lawyer. "Most everyone liked him."

Miller's friends were members of the Church of the Brethren, and no one was surprised when he became a conscientious objector after high school. Miller now says he made a mistake, having acted in blind obedience to his parents. No doubt, Miller was a bit naive. It wasn't until after he left high school for a small Brethren college, just across the fields from his parents' farm, that Miller learned about the Nazi extermination of Jews during World War II.

But Miller's old friends said they don't recall him ever talking about a change of heart in the past 20 years -- until he was nominated for lieutenant governor. "I was shocked," said one former classmate. "I couldn't believe Nathan would say that."

Miller's college scrapbook shows dozens of photographs of a jut-jawed state champion football player alongside many pictures of beautiful girls. "Nathan always cut a wide path with the girls," recalled Bowers. Indeed, over the years Miller has dated at least five Miss Virginias. But he never married, saying he couldn't spare the time from politics.

Miller was a student at T.C. Williams School of Law in Richmond, earning average grades, when he met lawyer Donald D. Litten. The head of his local draft board, Litten disliked conscientious objectors. But he hired Miller as a clerk after deciding "the boy didn't know what he was doing."

Miller turned out to be a wise choice. He was a workhorse with a pleasant temperament, always willing to do the most menial legal chores. And when local GOP officials sought a candidate in 1971, Miller turned out to be a wise choice again.

"Nobody else really wanted to do it," said Del. Clinton B. Miller, who is no relation to Nathan Miller but was his running mate that year. Although Nathan Miller wasn't even sure then whether he was a Republican or Democrat, he had extraordinarily marketable assets in the age of television politics: a warm, open, handsome face, a strong speaking voice, an impressive local athletic record and the same last name as then-attorney general Andrew P. Miller.

His first year in the statehouse, Miller introduced only two bills not requested by local governments: one to make it easier for farmers to dispose of dead chickens and one to help nearsighted people become truck drivers. Today, Miller cites as his greatest legislative accomplishment a bill that allowed people to share ownership of resort property.

Nathan Miller simply did not cut a wide path during his nine years in the legislature. "Nathan has not been an active legislator," said Sen. Wiley F. Mitchell (R-Alexandria), one of Miller's close advisers. "But he has introduced several bills of interest to his region."

Little noticed in the statehouse, Miller was an expert campaigner. George S. Aldhizer II, one of the Senate's most senior members, lost his seat to Miller after the young legislator repeatedly accused Aldhizer of a conflict because his firm was on a $100-a-month retainer with Virginia Electric and Power Company.

Between elections, Miller concentrated on routine constituent work, helping people get passports or car registrations. But it was campaigning, not lawmaking or constituent work, that made Miller's reputation. Time and again, he roamed his district, pumping hands at service stations and country stores. In 1978, Miller unsuccessfully sought the Republican nomination for the U.S. Senate. He lost, but it was that effort that brought Miller and Joe Loyacono together.

At first glance, Loyacono looks as different from Miller as Chicago street slang is from a mellow Virginia drawl. Dark and brooding, with a voice like squeezed lemons, Loyacono came to Charlottesville from the Midwest to run a political ad agency. One of his TV commercials advised voters to "cut the bologna" while a huge cleaver whacked through a sausage.

"Lo-WHACKono's ad," it was dubbed.

It was Loyacono who engineered Miller's unexpectedly successful campaign for the lieutenant governor nomination this year, pulling a victory out of a cliff-hanger convention when fundamentalist Christian candidate Guy O. Farley dropped out and most of his delegates refused to follow the leadership's candidate, State Sen. Herbert H. Bateman. That nomination won Miller more wrath from powerful party officials already miffed by his 1978 effort. They said Miller was too impatient for higher office.

"At 40 I'm impatient?" Miller asked angrily. "That's what they say, but that's because they wanted somebody else. It was convenient."

In the excitement of the convention, Miller came across as a religious conservative who appealed to Farley's supporters in part because Miller had run an upbeat preconvention campaign. But today, Miller is relying on the same kind of negative advertising that characterizes this year's statewide races.

For instance, Miller's ads juxtapose his 60-year-old opponent's age with his own "youthful energy," while other ads accuse Davis of championing tax increases and gun control. Recent polls show Miller and Davis nearly tied, but with about 40 percent of the voters undecided.

Miller is the more conservative candidate. He favors Reagan's budget cuts, the state's right-to-work law and a lid on state spending. He opposes the Equal Rights Amendment, an extension for the Voting Rights Act, gun control, state funding for abortion and collective bargaining for public employees.

Nathan Miller describes himself as a simple man who has amassed a $750,000 fortune by being a "workhorse, not a racehorse." He sees success as 1 percent inspiration, 99 percent perspiration. And he lives that way. One recent day he campaigned from 8 a.m. to midnight. He rarely reads books -- although he occasionally peruses the World Book Encyclopedia to relax. When he seeks advice, he generally turns to one of three people: his father, Litten or Loyacono.

Miller's philosophy of government is simple, too. Elected officials should carry out their duties as they see fit. If voters don't like it, they can vote them out. He is bewildered by all the fuss about his alleged conflicts of interest. He believes that legislators should be required to disclose their business ties, but that there should be no specific list of actions a member can or cannot take.

What is so wrong with helping a client in the legislature? he asked. The bills were good bills, he said. If voters believe he is giving his clients unfair advantage, Miller said, they have simple recourse: They can vote him out.

"It's a free country," Miller said. "They can elect whom they want to, and if they make a mistake, and if Nathan Miller's a crook and they elect him, then they've got him . . . We have an imperfect candidate, we have an imperfect electorate and we have an imperfect society. But it's the best that there is. It's sure better than Yasser Arafat, and it's sure better than Mao Tse-tung."