WHEN FORMER Virginia State Sen. Armistead L. Boothe of Alexandria visited the State Capitol last winter, he was ushered into the Senate chamber and introduced, as custom demands, by the senator who now holds his seat.

Then, unexpectedly, another senator rose to speak. This time it was 39-year-old J. Dudley Emick from Botetourt, who had been in high school when Boothe was fighting against efforts to defy desegregation by closing the public schools, an effort led by the Byrd organization that ran Virginia in the 1950s. With uncommon emotion, Emick said that Boothe had been one of his idols, that he had a rare sort of courage that inspired people like himself to get into politics.

"Daddy was really quite overcome by that," Boothe's daughter, Julie Perry, who was with him that day, said recently. "He was not always the most popular person in the Virginia legislature."

Boothe, a former state legislator, twice a candidate for state office, and a man who came to close to ending the Byrd organization's stronghold on Virginia government, recently ended his self-imposed political exile to accept the honorary chairmanship of a group fighting against proposals for racetrack gambling in the state.

That is why Boothe was in Richmond last winter to testify before a legislative committee, opposing a bill that would allow voters to decide next fall whether to allow gambling at horse tracks that would be built in Northern Virginia and the Norfolk area. The bill later was approved by the General Assembly.

Boothe is reemerging after eight years of private life devoted to raising money for the Virginia Theological Seminary, which is both close to his heart and to his home on Vicar Lane in Alexandria. His name is perhaps unfamiliar to many, but to political veterans in Virginia he represents a breed now nearly extinct and his presence is a reminder of things that might have been.

The breed is that of the true gentleman, the best of the Virginia tradition, a lifestyle of grace and modesty that requires both service and commerce, humor and gentility. Just as the antiques that fill Boothe's home are family heirlooms rather than items purchased at a nearby Antique Barn, so are his values and standards traditional and imbued with the patina of quality.

To know that this white-haired gentleman, wearing a navy tie embroidered with the names of his grandchildren and drinking tea from a fine china cup, once was called a radical, a liberal, a socialist, a commie, a tool of organized labor and the (heaven forbid) dreaded NAACP, is to know just how conservative Virginia is and was. Boothe, former Del. Edgar Bacon (D-Jonesville) said, is a man who was "right too soon."

"He was a moderate anywhere but here," his wife, Betty, said recently. "But in Virginia . . ."

In Virginia, those like Boothe who urged that the state comply with the 1954 Supreme Court decision outlawing school segregation were considered "ultra-liberal," to use the least abrasive of the terms the opponents flung at him. What they urged seems hardly dramatic by today's standards: compliance with the "law of the land" rather than acceptance of a series of laws pushed by the Byrd organization that formed the basis of Virginia's abortive policy of "massive resistance." The laws called for closing public schools rather than allowing them to be integrated and for spending state funds for private school tuition.

Boothe and a small band of legislators who resisted these proposals were bitterly attacked by the Byrd spokesmen. "They thought he [Boothe] was misguided, missed the boat somewhere along the line . . . [and was] probably overeducated," recalled former Gov. Colgate W. Darden Jr., himself a product of the Byrd organization. "There was a feeling he was a disrupter."

Despite the unpopularity of his position on closing schools and such other "radical" acts as proposing in 1950 that segregation on public transportation be abolished, or running in 1961 against Mills E. Godwin for the lieutenant governorship and in 1966 against Harry F. Byrd Jr. for the U.S. Senate, few could be more establishment than Boothe.

Now he comes forth to battle yet another segment of the Virginia establishment, the well-financed horse racing supporters who want tracks and gambling. Now a senior statesman, the emotion and turmoil of the past behind him, he is a frail-looking but energetic 71-year-old man whose very presence lends legitimacy to his cause.

"The horsebreeders are nice people, rich people," he says, "I can see how they'd want it. But I don't see why in our society today the people at the bottom of the financial pyramid should finance something for the people at the top - as nice as they are. Under this law they'd be very preferred people. This whole act was passed for the horsebreeders, a relatively small group who have millions of dollars. I like these people, they're great friends - but I don't think we should build up their business at our expense."

Boothe now works out of an office in his home, usually from 9 a.m. to 6:30 p.m. "I have to raise $1.4 million for the [seminary] library," he said. He has belonged to Christ Church in Alexandria since he was baptized there in 1908 (George Washington and Robert E. Lee worshipped there, too). Fulfilling a pledge made before undergoing heart surgery in 1969, Boothe gave up his prosperous law practice to raise money for the seminary. The first year he earned as much from the seminary. The first year he earned as much from the seminary as he had paid in taxes the year before.

The Boothes no longer play tennis on the courts that lie just beyond the backyard; a few years ago they gave the courts to daughter Julie and her family, who live next door. There are nine grandchildren, here and in Richmond and in Leesburg.Of their three daughters, two married lawyers and one an Episcopal clergyman. The daughters all attended private schools; the youngest had graduated by the time the schools were being desegregated in 1958.

Gardner L. Boothe, Armistead's father and chairman of the 8th District Democratic Committee for 50 years, is supposed to have said once that a "Virginia gentleman is a man who never bruises the mint in his juleps, walks his horse the last mile home, and slices his ham thin."

"That sounds like something he might have said," Boothe recalled, "But I don't know for sure if he did. Certainly he would have been kind to his horse, if he'd had any." Predicted Poll Tax Demise

BOOTHE WAS born and raised in Alexandria (later he was to counter campaign attacks on his Northern Virginia identity by pointing out that the region also was the home of such men as Washington and George Mason), and attended Episcopal High School. In 1954, his grandfather bought the building at 711 Princess St., now one of three offices of the Northern Virginia law firm that still carries his name. Another Boothe predecessor, Lewis Addision Armistead, was a Civil War hero, a fact referred to in numerous Boothe campaign speeches.

Boothe graduated from the University of Virginia in 1928, after five years in which he combined law studies with the general curriculum and earned a Phi Beta Kappa key. He took and passed the bar before leaving for Oxford University, which he attended as a Rhodes scholar. While he was there he met his wife, then Elizabeth Ravenel Peele of Chevy Chase. They were married in 1934, as yellowed news clippings of the time noted, at All Souls' Memorial Church.

"Later Mr. and Mrs. Boothe left on a short wedding trip, the latter wearing a smart ensemble of brown trimmed with white pique. In the fall they will be at home at 211 South Pitt St., Alexandria, Va."

During World War II he served in the Navy in the Pacific, where he encountered Byrd Junior, who, according to an often-told story, persuaded Boothe that on his return to Virginia he should get into politics and run for the House of Delegates. He did, successfully, in 1948, and joined Byrd in that state eight years later.

In 1949 Boothe wrote an article for the Virginia Law Review entitled "Civil Rights in Virginia," which formed the basis for his belief that legal segregation of the races was doomed.

He predicted the demise of the Virginia poll tax in 1950, 16 years before it was declared unconstitutional by the Supreme Court, and noted:

"It will be our duty to the past, the present and the future to recognize and foster equality of opportunity in employment, education, housing, and health among all our citizenry, regardless of race or color. We must think. We must act. We can not continually exclaim against the federal government usurping the powers of the state without exercising those powers ourselves as our responsibilities require."

To avoid an "era of chicanery, hatred and violence," he said, Virginia must prove to the U.S. courts and Congress that its intentions were to allow all races the rights guaranteed by both the state and federal constitutions. A Shot Through the Window

IN THE following years, Virginia was not only to attempt to defy the 1954 decision, but to enact laws designed to thwart the NAACP and to make registering to vote a major feat ("one of the silliest and most asinine pieces of legislation in our history," Boothe said during the 1961 campaign).

"It took an amazing amount of courage to take that position [to keep schools open] at that times," said Emick, whose retired law partner, Stuart Carter, was one of those who tried. "Particularly with James J. Kilpatrick writing editorials in the Richmond paper every day about how you should be taken out and strung up, and people writing you letters saying they'd like to see you dead . . ."

During the 1961 campaign for lieutenant governor, someone - it was never determined just who - fired a shot through the living room window of Boothe's 10th District coordinator, Marion Galland. During the 1966 campaign against Byrd - which Boothe lost by a frustratingly few 8,225 votes - the campaign held one of the first interracial campaign meetings ever, in Danville.

"It was in the basement of a church," recalled former Del. Ira M. Lechner of Arlington, who was Boothe's campaign director. "I remember we were pursued by the Klan in cars behind us when we left . . . He [Boothe] would never let us talk about it [publicly], but people were having their loans called in, their country club memberships threatened [for supporting Boothe]. People literally would shut the door in my face, they were so afraid of the [Byrd] machine. They'd try to give me cash to take their name off the list of supporters, and then say, 'I'm supporting him but I can't let anybody know.' People who are judges today would refuse us! Then their wives would write and say, 'I don't care what my husband says, I'm voting for you." . . . The Byrd machine knew that if we won it meant the end of their total domination of the state."

The 1966 campaign was also the victim of disorganization. Boothe ran it, largely out of his home. "It was one of the last of the good old fashioned campaigns," said daughter Julie, who worked in it. "Daddy didn't understand things like press releases. He figured if you had a good speech someone would be there to cover it. It wasn't until the last weeks of the campaign we persuaded him to let us do press releases."

Lechner recalled that the major direct-mail effort of the campaign, a newspaper-type tabloid, was prepared entirely by hand, and it took volunteers weeks to address more than a million copies. "Army had an editorial he wanted in it; it was dull as dishwater, but we couldn't persuade him to cut it or leave it out," Lechner said.

The editorial, again reflecting a man ahead of his times, urged U.S. recognition of Red China.

As a boss, Lechner said, Boothe was "very formal. Very charming. He'll call my home in the morning and say to my wife, 'Miz Lechner, is your charming husband awake and ready to spend a few moments in discussion with me?'" A "Liverly" Campaign

THE LYNCHBURG Daily News accused him in an editorial of having a "socialist philosophy," and said he had "an utter disregard for the fact of present federal domination through rape of the Constitution."

Boothe's response was: "Ingeniously woven throughout this laudatory editorial are adjectives and nouns which associate me with misrepresentation, which as a lawyer I midly resent, perversion, which I deny, socialism, which I do not espouse, demagoguery, of which I am not guilty, and rape, of which I am not capable."

It was as the cliche goes, a "lively" campaign. And when the returns were in, Portsmouth lawyer William B. Spong had triumphed over 70-year-old Willis Robertson in one Senate contest and "Little Harry" escaped from Booth more or less intact in the other. The last week of the campaign, Harry Byrd Sr. lay in a coma in Winchester, his con cancelled all campaign appearances, and Boothe did the same.

"Byrd learned from that campaign," Lechner said. "He'd been a rather abrasive leader of reactionaries in the state Senate. After that campaign he became sort of a neuter, so enmity for him has declined. [Retiring Republican Sen. William L.] Scott has upstaged him as the man to hate."

In 1976 Boothe endorsed Byrd, who by now was officially an "Independent," in his race against Democrat Elmo R. Zumwalt, a move that disappointed many to whom Boothe had been a hero. In Boothe's view, it was a pragmatic decision; Zumwalt, he said, did not have a chance, and Byrd had voted the right way on some legislation relating to contributions to charities.

"He [Boothe] was always a middle-of-the-road man," said fellow legislator Edgar Bacon. "I don't want to say anything that might be construced as hateful, but I think Army felt that the election of Byrd would cause less disruption and follow a tried and true path. The election of the admiral would have been a disruption; 1966 was far different, it was a question of a different program from Byrd's, but not a complete departure in the sense of the Virginia tradition."

Armistead Boothe himself seems to feel that talking about himself and rehashing the past is something he would rather not spend time on. He is more interested in the future, in the seminary and the fall campaign against pari-mutuel betting.

His political descendants, the men who are active today, are humorless technocrats. The last two charismatic types, politicians who could arouse strong emotions, were Henry Howell and Linwood Holton, and both have been banished within the last year, one in an election and one in a political convention. Virginia's position as one of the most conservative states is secure. The Democratic Party has not won a U.S. Senate seat since Spong's victory in 1966; the Republicans now hold six of the 10 congressional seats and two of three statewide offices.

Bill Spong said the other day that Boothe "would have made a marvelous minister . . . I don't mean that to be misinterpreted. It's that very often his beliefs have been very idealistic." Spong declined to speculate much on the unfulfilled possibilites of the past, but said he was writing a book about Virginia politics.

It's called "No Room in the Middle."