There were very few Arabs on the prairies of South Dakota in the 1930s, so no one knew what to make of James Abourezk, the son of a Lebanese peddler. "Kids used to beat me up and call me a goddamned black Jew," Abourezk says. "I'll never forget that."

Now he wears his past like armor and has become one of Washington's most passionate defenders of the Arab cause. A lawyer who has represented American Indians and the Ayatollah Khomeini's Islamic Republic of Iran, Abourezk is also known for his 1978 decision to quit the U.S. Senate. Now, the Lebanese war has sent him on a new public relations campaign.

Several weeks ago, he bought a full-page, $22,000 ad in The Washington Post that announced "Israel is Killing Lebanon," and then, four days later at a press conference for the American-Arab Anti-Discrimination Committee, said the Israelis have "imitated the methods and the means of their tormentors in Nazi Germany." A decade ago, he eloquently spoke on Capitol Hill about "an even-handed policy for all countries in the Middle East."

Many in Abourezk's circle wonder what happened. Ask him who his friends are and he'll mention a dozen or so, then say: "And the enemies? Everybody else."

Bethany Weidner, a former staffer, says, "I don't think he's any different than he was . . . Jim just sees the world divided into the screwers and the screwees," but others who have broken with him use words like "wacky," "nutty" and "poor Jim." Some say his anti-Israeli government position has gone all the way to anti-Semitic; Abourezk calls that a "great ploy of people who support Israel." Or as his friend Saul Landau says: "I don't think there are any Jews who don't pick up anti-Semitic vibes, if there are any. And none come from Jim." (Landau is a senior fellow at the Institute for Policy Studies, a left-leaning think tank critical of Israeli policy toward the Palestinians.)

Abourezk has cousins in Beirut, and he heard this week that they're still alive. Tanks rolled through the narrow streets of his parents' old village, tearing down houses as they passed. Four died. Abourezk, like many others, is captured by the emotion of Lebanon.

But in the past weeks, Abourezk has had the peculiar experience of watching the world of Washington opinion move closer to him. Close, but not too close. Many criticize Menachem Begin, but few go so far as to say that the Israelis are "conducting a propaganda campaign that would make Joseph Goebbels proud." Remarks like that have cost Abourezk a number of former South Dakota supporters who, in the words of one-time Aberdeen fund-raiser Manley Feinstein, consider him a "turncoat" with "as many moral scruples as a skunk."

Abourezk's reaction to the imbroglio? "I frankly don't give a damn," he says.

"He's not being honest with himself when he says that," says U.S. Circuit Court of Appeals Judge Abner Mikva, a former Abourezk colleague from the House. "I think he's probably grown used to it. Once we had a meeting in Illinois when he was raising money, and the questions were getting pretty sharp. And I remember being in the Capitol with him, chatting for a minute or two, and I asked, 'How's it going?' And whatever he said, it was clear that he was depressed. I made some flippant remark and he said, 'Nah, it's really getting to me.' " Confronting the Past

People often discover roots late in life, but few do it because they've been elected to the U.S. Senate. "It probably all started when I made a tour of the Middle East in 1973, my first year," says Abourezk, 51. "I had a very dramatic experience when I went back to my parents' village in Lebanon. It's called Kfeir, about 10 to 15 miles from the Israeli border . . . there was a canvas banner put out along the road, right near a bomb crater made by Israeli warplanes. In Arabic it said, 'Welcome Sheik Senator James Abourezk.' And in English it said, 'Phantom jets made in U.S.A.' There were about 3,000 people turned out, and then the mayor of Kfeir got up and made a speech, and it was sort of a trauma for me. I mean, I'd heard about the village from my parents for a long, long time. The mayor's speech basically went like this: 'We have always thought of the United States as the protector of liberty, but American bombs have been dropping on us, killing our people. Now we think the United States is a dictator.' And looking back, it was a series of things like this that were happening to me personally."

"It was a quick thing," says Pete Stavrianos, Abourezk's former administrative assistant. " 'What is ethnic background?' You see that in a lot of people. All of a sudden, they confront it."

On a recent Sunday, Abourezk was watching Menachem Begin on his kitchen television set and complaining that nobody on CBS' "Face the Nation" had stuck the Israeli prime minister with a tough question. Freshly showered after a morning jog, Abourezk lit up a cigar and took a few gulps of beer before pouring it into the fixings for one of his "Famous Omelets." The kitchen in his Connecticut Avenue co-op is one of a cook, filled with hanging pans and a Cuisinart for preparing his Middle Eastern dinners. He is a stocky man with hair that curls over the back of his collar. Even many who oppose him say they can't help but like him. "I'm in total disagreement with his stand on the Middle East," says Sen. Howard M. Metzenbaum (D-Ohio). "But that's never affected my warm feeling toward him."

Abourezk makes it clear that he is giving this interview only because he wants to publicize his cause. American newspapers, he feels, are fiercely biased toward Israel.

In the past year, Abourezk has divorced his wife and left his old law firm, Abourezk, Shack & Mendenhall. Of his 29-year marriage, he says, "It got worse and worse. Eventually, we just couldn't do it anymore." Of the law firm, former partner Tom Shack simply says "the relationship was dissolved by mutual agreement" and offers "no comment" on Abourezk's work.

Now Abourezk practices at Abourezk, Sobol & Trister. His new office is quiet and carefully appointed, decorated with a Persian rug and Bedouin blankets. There is a fine view of Dupont Circle. It is here, in an earlier interview, that he talked about what changed him.

"Abourezk never thought about the Middle East while he was a congressman," says Alan Baron, editor of a political newsletter and an old friend. "When he went to the Middle East as a senator, the Arab countries treated him as a hero. He started to look at the issue. Then, turning his back on the Jews produced, among the most ardent, a vehement response. I think that escalated his own rhetoric."

Others say Abourezk, as an Arab-American, more or less found the cause in his lap. "Yeah, that's probably more like it," Abourezk says.

Some former supporters are still vehement. "We feel betrayed," says Louis Hurwitz, a Sioux City lawyer who was an important fund-raiser for Abourezk. "He says he saw the light. Well, I think in large measure it's the influence of the Arab lobby and the fact that he's been on the payroll."

Abourezk won't say how much he makes or who his clients are, but he will say that "I'm not making gobs of money. I'm constantly in debt. I spend more time politicking than I do practicing law." (In 1973, he earned $49,425 for 14 speeches that year, including a $10,000 honorarium for addressing 1,000 Arab-Americans in Detroit.) Unlike Fred Dutton, the well-known and influential lobbyist for Arab causes, Abourezk is not a registered foreign agent.

"I'm sure he's made decent money since he's left the Senate," says Stavrianos. "But I'm sure he could have tripled it if he said, 'I'm going to be rich.' "

Abourezk grew up on the Rosebud Indian reservation, the third son of parents who ran a local general store. "I took care of myself," he says. "I went where I pleased and did what I pleased." Once he took his father's car to see a girlfriend 17 miles away; to make sure the odometer didn't register, he backed it all the way home. He was expelled his senior year for lassoing a teacher during a high school assembly and had to finish up by hitchhiking to school in a different town. "He was always full of the devil," recalls his brother, Tom.

He went to the South Dakota School of Mines and Technology, then the University of South Dakota law school. He was also: a bartender, a black-jack dealer, a used-car salesman and a judo instructor. He eventually settled into a law practice in Rapid City where he says he did a lot of pro bono work for the Indians. In 1970, he was the first Democrat since the Roosevelt landslides of the 1930s to win in the state's second district. Few thought he could do it. "Not even me," says Abourezk. He admits he wasn't a sophisticated politician. "Basically, it's all sort of an ego drive. I had ideas about how things were going to happen. I was against the war, and so on."

Two years later, when the incumbent retired, Abourezk landed in the Senate. He was seen as the renegade from the West, delighting the press with his outbursts yet infuriating his colleagues with an all-night, unsuccessful filibuster against attempts to deregulate the price of natural gas. The legislation he actually passed was minimal. In 1977, he announced he wouldn't seek reelection. "I can't wait to get out of this chicken---- outfit," he said at the time.

He said he was tired of putting politics over family and depressed about the compromising necessary to get elected. Skeptics questioned his motives. Friends and enemies in South Dakota said he would have had a tough time getting reelected, although he might have won if he'd hustled. But at that point, Abourezk didn't care.

"At first, he went at it like he goes at most things--just flat out," says Stavrianos. "Then he got tired of it, and started to resent it.

"His strength in the Senate," Stavrianos adds, "was that he really didn't give a damn whether public opinion sided with what he was doing. But if you wanted somebody who wanted to do a careful job of developing legislation, educating the public on the issue and working carefully over a long period of time, in detail, then he would be a hopeless failure."

"He found it offensive if a colleague asked him to keep his mouth shut on an issue now and then," Mikva once said. "And he didn't like sitting around waiting. He likes quick results, not fussing with commas and dots. He's just not a disciplined person in the legislative process."

Now, on Abourezk's pro-Arab stand, Mikva says: "He's wrong as hell on most of it--but I believe he means it. He's being very one-dimensional. At this point, he doesn't really understand the problems and the passions that motivate people, besides Lebanese, in that part of the world." Advantages of the Underdog

Since he left the Senate for private practice in 1979, Abourezk has spent much of his time giving pro-Arab speeches. He frequently mentions Abscam, the FBI undercover operation where agents posed as Arabs, as an example of racism. "How do you think Jewscam sounds?" he asks.

But there are some advantages to being underdog. "I think you do have a lot more freedom than most people," he says.

So is that why he likes this?

"It's not a question of like," he says. " 'Do you enjoy pain?' Nobody really does . . . If your conscience says something, and you avoid acting on your conscience for a long time, you have to do something to ease it. And if you're in a position to do something about it, then I think you ought to . . . When you think of the phonies up on Capitol Hill who'll fight to the death for wild horses or sperm wales--and not do a goddamned thing for a human being."

He says he doesn't feel "heroic" about any of this and, if the truth be known, would prefer to live in Sonoma County, Calif., with a small vineyard, a greenhouse and a job teaching government. "I guess if I had my druthers, I'd rather live peacefully and not be embroiled in controversy," he says.

He sighs. "But I can't afford it. I don't have enough money to get out of town."