For the 20 years that Walter Fauntroy has been a familiar face in Washington, one thing has rarely changed: his half-smile.

It's been a sunny signal of good will; a sign of confidence through political campaigns; a crafty, noncommittal reply to adversaries; a ready balm to the troubles and tears of civil rights workers; a persuasive tool to offset his lack a vote as D.C. delegate on Capitol Hill.

Now the smile has tightened. That playful twist on the small, flat face has almost disappeared. For the last 10 weeks, Walter Fauntroy, the city's senior elected official, has been experiencing the worst crisis of his public career.

He has been in the middle of public debate about the legitimacy and merits of his trip to Lebanon, where as chairman of the board of the Southern Christian Leadership Conference (SCLC), he met with Yasser Arafat, the head of the Palestine Liberation Organization. The trip triggered a whirlwind of anger among segments of his constituency, most vocally the Jewish part, helped bring out further antagonisms between the Jewish and black communities nationally, and ended up causing the most publicized schism among black leaders in recent times.

Whatever the outcome, the issues and the limelight have presented a test for Fauntroy, 46, who is now seen, for the first time, as vulnerable at the voting booth.

Though the pressures have shown in a certain weariness, people have observed, once again, that Walter Fauntroy is fairly imperturbable. "I don't accept the theory that I'm vulnerable. Our position will be vindicated," he says, with the mild testiness of a Baptist minister.

When he withdrew his invitation to Arafat to come to the United Nations under SCLC auspices, saying "he didn't meet us halfway," Fauntroy suffered an embarrassing episode of eating crow.

And that was quickly followed by Vernon Jordan and Bayard Rustin, longtime colleagues, attacking the SCLC's fact-finding mission. Jordan, without naming names, labeled the Mideast trips of Fauntroy and Joseph Lowery, and later Jesse Jackson, as "sideshows" and "ill-considered flirtations."

Fauntroy's tensions surfaced. At a ground-breaking ceremony at his New Bethel Baptist Church upon returning from lebanon, Fauntroy buckled from fatigue and an intestinal virus and was rushed by ambulance to a hospital emergency room.

His semons, says his assistant pastor, Rev. James Jones, have had an urgency since his return.

"Every once in a while you can sense from his sermons that something is pressing him," said Jones. "Now on the overseas situation, he used scriptural references. He talked about Andrew Young and said there was no harm in his position -- being an ambassador of the U.S. and an ambassador of the Lord. He said above all that he [Young] is an ambassador of the Lord."

Fauntroy remains undaunted. At home, says his wife, Dorothy, he finds comfort in prayer and fasting. Publicly he seems to relish the fight.

"So let anyone who wishes run against me," he said at one point. "Let anyone who wishes withdraw his support. It doesn't matter to me."

It had to be Fauntroy's worst moment on Capitol Hill in the last 10 weeks. Maybe ever.

At 7 o'clock one evening, Fauntroy was granted 60 minutes to tell his House colleagues about his trip to Lebanon. Hardly had he started his review of the SCLC's work when Rep. Jack Kemp (R-N.Y.) began interrupting, asking about the PLO and Israel's right to exist. Kemp's voice sounded edgy. So did Fauntroy's.

After his summary of the trip, Rep. Millicent Fenwick (R-N.J.) got into a long, pointed exchange with Fauntroy.

Speaking of Arafat, Fenwick said: "I do not think Dr. Martin Luther King would have sat down with him for one minute." Responded Fauntroy: "Oh I know that he would."

Fenwick: "I do not think so."

Fauntroy: "I know he would."

Fauntroy was on the hot seat again in the Senate Caucus Room with a group of Jewish senior citizens who had come to Capitol Hill to discuss foreign relations with several congressmen. Fauntroy became their target. "The Jews died for you in the South," one said. "That was not the PLO, that was [civil rights worker] Andrew Goodman."

Fauntroy stuck to his argument that peace would only come through direct talks with parties such as the PLO. The senior citizens left unconvinced; Fauntroy was visibly shaken by the suggestions that he didn't care about lives lost in the civil rights movement.

The discussion, as defined by commentator Carl Rowan, would be about the "bitter public disagreements" among black leaders. Before the taping, Fauntroy, Jesse Jackson, Benjamin Hooks and Vernon Jordan momentarily covered their strained relations with some slap-happy joking. As they tested the mikes, they joked about Fauntroy's singing.

Once on the air, they began, politely, to disagree. Fauntroy felt that the discussion had bogged down on the issue of who was getting money from the Jews and Arabs, and said, "I'd like to move beyond the question of money."

Rowan snapped, "I'll you when to move."

After the taping, Fauntroy left frustrated, feeling, that he could not get his message heard.

Fauntroy sat in his Capitol Hill office, appeaing weary. Before him was a notebook of points he wanted to make about his recent excursion into diplomacy. The only sign of light-heartedness in a man known for his buoyancy was an aside about his "bragging wall of plaques."

There was none of the fighting exuberance that marked Fauntroy on his first day back from his four-day trip to Lebanon when, trailed by network camera crews, he was jocular and pointed.

"Nothing that anybody has said to me has changed my opinion of the basic intelligence, the basic wisdom and the soundness of the position we advocated," he said. "Even it I were spiritually and morally strong, and if I couldn't rationalize it intellectually, I would have problems. But I have no problems, reconciling my moral views, my moral commitment, to my intellectual perception."

He knows that his stand is unacceptable to some key constituents and that his involvement in the Mideast crisis is potentially damaging to his career.

But he has braced himself with the comfort that he was there when Martin L. King, Jr., decided to take his stand on the Vietnam War and Red China in 1967 and history proved the stand right.

The only time Fauntroy does not refer to his notes, the only time there's a measure of unrehearsed emotion, is when speaks of the challenge of King's credibility over the Vietnam issue.

"Indeed, I felt a sense of guilt that the black nation generally and whites of good will had rejected Dr. King's initiatives and made his last year of life a tormented one," he said, explaining his willingness to rise to Andrew Young's defense and to risk his own solid base.

After the Young resignation, Fauntroy promptly defended him. Fauntroy sidestepped the instant rhetoric about a Jewish-black rift and went into seclusion for six days, studying the Mideast questions. Then he became a spokesman as civil rights leaders met with Palestinian and Israeli officials at the United Nations.

Now he turns to a window, seemingly lost in thought, and says, "It's very lonely out there."

This is not Fauntray's first crisis.

But in the last year the complaints about his leadership have changed from pure personality differences to accusations of inept politics, bossism, a napoleonic drive.

The charges are based, first, on his role in last year's District mayoral elections, the fact that he asked Marion Barry not ro run for mayor, choosing to endorse Sterling Tucker's candidacy. Some thought that in doing so he was opting for continuation, not change.

Various groups have resisted his management of the national effort to get the D.C. Voting Rights Amendment passed.

And, because Tucker lost, and because the Voting Rights Amendment appears to be stalled, and because the joint lobbying of Fauntroy, Barry and Arrington Dixon to get a black appointed U.S. attorney for the District failed, Fauntroy's opponents say he is on the wane.

But friends say Fauntroy will survive; a recent poll says that he will sail through reelection next year and that the constituency rift will be mended.

On Thursday, Joseph Danzansky will give a support party for Fauntroy -- where Andrew Young, the man whose resignation sparked this whole political test for Fauntroy, will speak

One of the lobbying tools Fauntroy uses is a system of index cards, handed out to allies on Capitol Hill. The cards contain four or so names, targets for lobbying. "How are you doing on your list?" is now a familiar Fauntroy greeting. If the colleagues have misplaced their cards, Fauntroy has 10 duplicates ready. In the home rule battle, this system, and the network carefully cultivated from the civil rights legislative experience of the 1960s, worked.

Another example: When the push for home rule started eight years ago, Fauntroy took busloads of local supporters down to South Carolina to support a black candidate who was challenging the crusty overlord of the House District committee, John McMillan. On the second try the strategy worked, and Fauntroy celebrated with a motorcade through Washington, calling out, "Johnny Mac won't be back."

Another conversion, which Fauntory considered a major victory, occurred last year when he gained Sen. Strom Thurmond's (R.-S.C.) support of the Voting Rights Amendment. When Thurmond said, "I'm behind you," Fauntroy immediately asked him to lobby with some other Deep South senator. Reporting back, Thurmond said that most of them had been reluctant but that he persuaded them by saying, "Do it for Strom." Fauntroy enjoyed telling the tale, regaling his staff with his imitation of Thurmond.

And in the last minute effort on the House floor, Rep. Don Edwards, (D-Calif.) the floor leader of the bill, recalled, laughing: "Walter used muscle. He was talking casually to a member from the South and all the while he was fingering some papers.Walter said, "Sure hope you can help us.' And the guy said, 'I don't know," and then asked what was in Walter's hands.And Walter said very quietly, "It's a list of phone numbers of the black ministers in your state."

Fauntroy is clearly a political force. At the press conference last year, when he announced his support of Sterling Tucker's candidacy for mayor and urged Barry to give up his ambitions to be mayor at the time, Calvin Rolark, the gadfly local publisher, asked him, "Do you really want to be a Big Daddy?"

The charges of bossism date to the 1972 Democratic convention, when Fauntroy, who was running as a favorite-son candidate, had pledged to keep his slate uncommitted. Then, in a surprise move, he changed his plans, committing the delegates to George McGovern.

"As far as I know it was done totally on his own. So I considered it less than honest," says william Lucy, then head of the then-called Demoratic Central Committee. "It left me with the feeling he was an opportunist."

There have been other signs that Fauntroy likes to flex his muscle. During the delegate selection process for the 1976 convention, Fauntroy asked for a number of delegates he could pick. And when the selection for delegates to the Democratic midterm convention last winter came up at the local party's meeting, Fauntroy asked to be elected.

Rev. David Eaton, Fauntroy's friend from schooldays at Shaw and still his confidante, sees Fauntroy as a power-broker, not a boss.

"Bossism? If he wanted, he could have run when Cliff [Alexander] ran for mayor. He could have run when Sterling did," says Eaton. "If being a powerbroker means getting people in the right places and getting humanistic change, then he's a powerbroker."

On issues other than Mideast diplomacy, Fauntroy gets good reviews from most colleagues.

Fenwick, Republican member of the House District Committee, calls his manner "winning, personable, tolerant, extraordinarily tolerant." Before the Mideast question, she says, their disagreements were "most mild."

Stewart McKinney (R-Conn.) the ranking Republican on the committee, says, "He's a very effective urban voice, and there are darned few of us."

A product of the Shaw community, the grandson of the neighborhood matriarch everyone called "Big Momma" and a feisty scholar at Shaw and Dunbar, Walter Fauntroy is a genuine homeboy.

Few other politicians in Washington can make that claim.

Fauntroy grew up on Westminster Street, long a self-contained community of neat row houses and lampposts, with a tradition of community service. William Fauntroy, a worker at the U.S. Patent Office who worked up to a GS-5 in his 40 years there, and his wife, Ethel, had seven children. One neighbor remembers, "We were all so poor, we only spelt it with one 'o'." oOne child was stricken with polio.

When his reputation as a small, quiet, studious kid made him the target of neighborhood bullies, Fauntroy took up boxing. Another neighborhood youngster later to achieve success, singer Marvin Gaye, was often a sparring partner.

When his younger brother, Raymond, had his first battle with racism, Fauntroy, then 17, reacted stoically. "I entered a soapbox derby with this car we had worked on all night at the 12th Street Y," said Raymond, now head of the Miami-Dade County SCLC. "This white man came along and tightened my wheels so tightly I could hardly move. When Walter saw the tire, he protested to the officials,and they just ignored us. And Walter, though he was very upset, just said we could wait until the next time."

In the early 1950s, when Fauntroy was going off to Virginia Union University, thus becoming one of the first Shaw youngsters to go "away" to college, there was an outpouring of financial support, one contemporary recalls: "Such frying of fish and chicken you never saw."

When he returned from Virginia and Yale University Divinity School, he went to his neighborhood to work at New Bethel Baptist Church. By then the look of Walter Fauntroy that became so familiar over the next 20 years was fixed: the pear-shaped face with the quizzical eyebrows, the traditional, close-cropped hairstyle and the strong, high-pitched tenor.

"What you see of Walter has always been. He smiles a lot, and that's always been Walter. That is not a public pose," says a childhood friend, Erlena Bland.

In the next few years Fauntroy built his political base and enlarged his philosophy. He fitted it with the activist litany of the period, joining the SCLC and heading its Washington office. He started his own community group, the Model Inner City Community Organization, and the Coalition of Conscience, with Marion Barry, Channing Phillips and the late Ralph Featherstone.

Once when Martin King was speaking on the steps of Shaw Junior High, recalls Petey Greene, a group of rightwing protesters stood across the street yelling "Martin Luther Coon." Greene and his boys wanted to rumble but Fauntroy stopped them, saying the picketers had their rights.

The visibility Fauntroy gained as King's Washington representative and coordinator of important 1960s civil rights events, including the March on Washington in 1963, helped him to an appointment on the city's first City Council. "He did a good job with the White House conference," recalls Army Secretary Clifford Alexander, then a White House assistant. "He was not anybody's patsy, and the conference was marked by dissension. But Walter was a faithful conduit of all sides."

When the jockeying started for the job of D.C. nonvoting delegate, Fauntroy was the anxious strategist out the reluctant candidate.

"Marion and Walter wanted me to run. Then we decided it wasn't my temperament," recalled David Eaton. Sterling Tucker, who also declined to run, said, "Walter was reluctant because he wondered whether or not it would be misleading for people to think they had a congressman, and we told him home rule would be the goal."

In Congress, he steadily made his presence felt and, in a particularly satisfying moment, shared embraces with Walter Mondale, Ted Kennedy and Birch Bayh over the Voting Rights Amendment victory.

There's a consistency and a certain rigidness in the world around Walter Fauntroy. For his own comfort today he has recycled the words he spoke to King when his public stands were criticized. "Back in 1967 I shared this with Martin, the words of a British Methodist minister, who said, 'On some issues cowardice asks the question: Is it safe? And vanity asks the question: Is it popular? Expediency asks the question: Is it politic? But conscience asks the question: Is it right?"

The smile, as Fauntroy fingers the well-worn pages of a Bible, is full of satisfaction.