"THIS IS one of our favorite presidents," said Libertarian candidate Ed Clark, pointing to a plaster bust of Chester Alan Arthur that rested amid the clutter on his campaign manager's desk. "He did very little."

don't feel sorry for Ed Clark. He's running for president, and he knows he's going to lose. But he is not a lonely hoot owl howling into thenight, hoping that somehow seas will part or mountains fall, and he will walk into the White House.

He's selling ideas, and hoping to promote a party that has gone, in nine years, from being obscurity to a curiosity to respectable recognition. The Libertarians have elected a state legislator inAlaska, and have former Sen. Eugene McCarthy, the politicalchameleon of the year, speaking up for them in television ads. (This did not, however, deter McCarthy from endorsing Ronald Reagan.)

"I'll vote for him," a student at American University was overhead to say to a companion after a recentClark speech. "My mother and father are Libertarians, too."

"You're father?" asked his friend. "Doesn't he mind about the marijuana?"

No, the friend was assured, his father didn't mind that the Libertarians favor legalizing marijuana.

For the banner carrier of a party supporting legal pot and other expressions of individual freedom, Clark looks quite prim. He's a middle-class, button-down anti-trust lawyeron leave from Atlantic Richfield in Los Angeles. He lives,he said, a very conventional life, and the only drugs he uses are "Coca Cola, cigarettes and California wine."

He does not see himself as a quixotic figure. An election should not be just a horse race, he and his aides say stiffly. "Itshould have some ethical, moral or philosophical basis." What they propose to offer is nothing less than changing the course of American policitics, by challenging the dominance of the two major parties and "establishing a three-party America in 1980."

Neither is he charismatic, but rather, appropriately low-key for a party that isn't "into the leadershipprinciple in politics." The son of a small-town lawyer in Massachusetts, Clark, 50, was a disaffected Republican when he read about the formation of the Libertarian party while riding to his New York law firm on the IRT eight years ago.

"I voted for Nixon in 1960," he said. "In 1968, I just couldn't bring myself to vote."

His views evolved over time, through college at Dartmouth, law school at Harvard and service in the Navy. He worked for several law firms and on hisown before joining Atlantic Richfield, married a few years ago and has an adopted 6-year-old son he dotes on. The campaign is a "family project."

"I view World War I as sort ofthe watershed of Western society," he said. "Before World War I, the world was becoming more libertarian in the sense of free-market liberties and a democratic society. Then, afterwards, it started going downhill. The problem still is the thing that caused the massive destruction of World War I -- bigger and bigger government and more and more nationalism. If you're going to combat that sort of state worship -- which has sort of replaced religion as our real religion -- you have to have some sort of ideological or philosophical base to do it. The individual rights basis, which is the libertarian party basis, is the right way to go."

He remembers his father telling stories about prohibition, "which, in his view, had corrupted and subverted the whole legal system . . . alcohol consumption went up, thousands of people were killed by contaminated alcohol. It didn't stop over-consumption of alcohol. It was just a disaster."

"We [Libertarians] believe in laws that protect children, but with adults we believe in Locke's theory that you own your own person. You may use your body any way you wish -- even for people whodo things that other people might think is bad for their bodies. For example, chocolate cake in excess is bad for yourbody, but we don't ban that."

There is, of course, the problem of balancing competing rights, In a campaign book, Clark noted that, while he believes that discrimination againsthomosexuals should be erased, the rights of parents who do not want their children taught by them must also be acknowledged. "Although I recognize the problem, I am afraid that, at this point, nothing can be done about it . . . We favor maximizing voluntary as opposed to coerced interactions among people . . . thus we strongly oppose any legislation forcing the individual who is prejudiced against gay people to employ them in a private business, rent or sell an apartment house to them, or allow them into his establishment. In particular, private schools should be free to make whatever rules they wish on the subject."

Some call the party's views conservative, some call them liberal. That's one of their main attractions -- they appeal to the person who types himself as neither. Their proposals include:

Cutting income-taxrates in half, abolishing inheritance and gift taxes and customs duties, and raising to $7,500 a year the income level at which people pay no taxes.

Cutting $200 billion from the federal budget, including abolishing the Department of Education.

Allowing a $1,200 tax deduction on tuition paid to a private school, per student under 2l, and allowing $1,200 tax credits for people who take care of aged or disabled family members.

Eliminating social security taxes and benefits for everyone age 40 and under.

Withdrawing from NATO and other mutual defense organizations.

Ending all foreign aid and eliminating all trade barriers.

Withdrawing the CIA from foreign countries.

Withdrawing military troops and bases from foreign countries.

Legalizing marijuana,prostitution and other "unagressive" crimes.

The campaign has been largely focused on media, both paid and free. Almost two-thirds of the expected $3 million campaign fund hascome from the vice-presidential candidate, David Koch, who is taking advantage of the election law that allows a candidate to contribute as much as he wants to his own campaign.

Clark travels around by commercial airline, accompanied byone or two aides speaking at colleges and clubs and trying to get interviewed as often as possible. Last Tuesday, for example, he started with a press conference in Chicago and aspeech to the Board of Trade, where l05 of its members endorsed him, flew to Washington for a press conference, flew toNew York for another, and to Boston for a speech at the John F. Kennedy School of Government.

He was not included inthe debate between Carter and Reagan, but, nonetheless, campaign co-manager Edward Crane said he won. "Those two were such losers that Clark won by default," he said.

Crane said the Libertarians, having achieved their first goal of getting on the ballot in all 50 states, expected to get media coverage worthy of a credible third party. But John Andersonknocked them off the screen, a blow they consider unfair, and siphoned off contributions they might have gotten. Anderson, they say, is a "conventional liberal" who is not building a lasting party structure that will offer alternatives inthe future; The Libertarian Party, they reason, is a growing third party for which a vote would not be merely a protestbut an investment.

In 1978, our candidates got more votes than all the other third-party candidates combined," Cranesaid. "We don't view ourselves as some sort of curiosity trying to get publicity . . . it's possible we can change politics in this country. We've had solid growth; when people become convinced of the Libertarian approach they don't change."

The party has 550 candidates running for local, stateand federal offices, Crane said, and is hoping that Clark will get enough votes to get permanent ballot status in two-thirds of the 50 states (requirements vary between l percent and l0 percent of the vote in different states.)

The typical Libertarian, he said, is younger than average, poorer, better educated, and more often white than black. They are quite popular on college campuses.

"It's no fun working in an environment where you know when the votes are counted you're not going to be on top," Clark said. "But I don't take the view, like the other small parties, that you get on the ballot just to get your views out there. You've got to be able to affect the outcome and the direction of elections. And, I think we're going to get double-digit percentages in some of our states and congressional races.

"The campaign has been a tremendous success," he said, almost cheerfully, "in terms of having the American people aware that there's a new political party out there and that we're not subversive.