Mitch Snyder, 46, who was found hanged yesterday at the shelter he established in downtown Washington, was a single-minded, charismatic and visionary social activist who made the homeless a part of the nation's unfinished business.

An ascetic, impassioned man who dressed in donated clothes and often slept on grates as a gesture of solidarity with the unfortunates for whom he worked, Snyder made his name and his cause known in the highest reaches of the government, including the White House. His organization was the Community for Creative Non-Violence, of which he had been the leading figure in recent years, and his chief weapon was the fast.

He was unsparing of himself in his use of it, and at different times he directed it against targets as diverse as a prosperous Catholic parish in Georgetown and the national government.

In 1984, he fasted for 51 days to compel the government to turn over to the CCNV a dilapidated building at 425 Second Street NW. Two days before the presidential election, and with "60 Minutes" poised to bring the dispute to a national television audience, the Reagan administration announced that it would make the gift and that $6 million would be spent to turn it into a model facility for the homeless. When delays developed, Snyder fasted twice more.

During the same election season, he campaigned for District voters to pass a referendum called Initative 17, obligating the city to provide shelter for every homeless person. The measure was the first of its kind in the nation. On June 26 of this year, the D.C. Council voted to reduce services provided under the program because of the cost.

Lionized by some as a savior of the poor and the downtrodden, Snyder was denounced by others as a publicity-hungry gadfly whose hunger strikes were a form of political blackmail and whose programs were more rhetoric than substance.

His answer was, "When you represent powerless people, you have to fight every step of the way."

The 1984 strike and its outcome made him a national figure. In addition to being on "60 Minutes," his story was told in a television film called "Samaritan: The Mitch Snyder Story." Martin Sheen, who played the title role, called him "a saint." In 1988, Washington filmmaker Ginny Durring made a documentary about him called "Promises to Keep," which received an Academy Award nomination.

In addition, there were speaking engagements, fund-raising events, and much attention from the media. He was on the Geraldo Rivera show and many others. At one occasion, the guests included Valerie Harper, Eunice Shriver, Jack Valenti and members of Congress. He met Jane Fonda.

At Christmas in 1987, the CCNV received a $5,000 donation from the Soviet Peace Fund.

The man who did these things was born Mitchell Darryl Snyder in Brooklyn, N.Y., and the first 25 years of his life were spent on an entirely different course than the one that made him famous. He attended Erasmus Hall High School in Brooklyn, but dropped out. He turned to breaking into parking meters and was sent to a reform school.

On Oct. 13, 1963, he married Ellen Kleiman, now Ellen Daly. He was so short of money during their courtship that she generally had to pay when they went to the movies. Sometimes they would go to Union Square, the place where soapbox speakers congregate in New York. "All of a sudden he would get up and start to talk," she told The Washington Post in an interview in 1988. "It was more or less about communism and politics and all that. He could draw crowds. He was always able to draw crowds."

But there were few signs that Snyder would become a social reformer. Instead, he went to work selling vacuum cleaners and other appliances -- "He could sell anything because he had the gift of gab," his wife said -- and the couple had two children, Ricky and Dean.

When Snyder couldn't make enough to support them, he started cashing bad checks. In 1969, he left them and went to California. In 1970, he and a check-cashing companion from New York were arrested in Las Vegas on a charge of stealing the car in which they were riding. Snyder was sentenced to three years in the federal prison in Danbury, Conn.

While he was there, his wife visited him every two weeks, and the plan was that they would start over when he got out. Then, one day Ellen got a call from prison officials telling her that Mitchell, as she called him, was on a hunger strike to protest the use of "tiger cages" by the United States in Vietnam.

Ellen Daly said this behavior seemed entirely inexplicable -- what did it have to do with the wife and kids in Brooklyn? -- and that it jeopardized his chances of winning parole.

"She basically wanted me to be like other people, and I basically wasn't like other people," Snyder told The Post.

In fact, he served his full sentence at Danbury. When he was released, it was apparent that the marriage was over.

What had happened to bring about so radical a change in Snyder's perceptions was that he had met the Berrigan brothers, Daniel and Philip, the Jesuit priests who had been jailed for destroying draft records. They turned him to social activism. He led his first hunger strikes while still in Danbury, and he said they gave him a "sense of power."

In 1973, Snyder came to Washington. He joined the CCNV, which had been founded by Edwin Guinan, a former Paulist priest. He first came to public attention on Christmas Day, when he and a companion were arrested for climbing the White House fence to protest the war in Vietnam.

By the mid-1970s, Snyder was concentrating on the homeless as his chief issue. His first widely publicized fast occurred in 1978, when he took on the parish of Holy Trinity Catholic Church in Georgetown.

While attending Mass there, he heard the priest praise his work among the poor. So he asked the parish for a donation. When it refused, he began a hunger strike that lasted 51 days. Finally, church officials seemed to relent. But when money was not forthcoming after several weeks, Snyder began another fast. He called it off when parishioners voted not to cave into his demands.

Snyder said he wished to bring the plight of the homeless to the attention of prosperous people of Georgetown. Many of the parishioners and their legal advisers said he was trying to blackmail them.

Snyder's most recent cause was opposing efforts by federal census takers to count the homeless. He said the count would be too low and that it would be used to make policy decisions that would not meet the needs of the disadvantaged.

This spring, he announced he would take a leave from CCNV and go on an extended retreat at a Trappist monastery in Berryville, Va. "I'm a religious person, and from time to time it's important to renew our relationship with God," he said. He said he wanted to meditate and "do simple work like baking bread."

He also announced that at the end of the summer he and Carol Fennelly, his companion and colleague for 14 years, would be married.

In 1985, after 15 years in which he had never tried to contact his wife and sons, Snyder received a telephone call from Ellen Daly, who said she had seen television coverage of his 1984 fast. As a result, he was able to meet his sons. He agreed to contribute to their education and he and his former wife became friends.

Snyder said in 1988 that abandoning his family had caused him great pain over the years, but he had been unable to do otherwise. He offered this assessment of his life:

"I don't consider myself a good person. I tend to be very impatient, I tend to be very short, I tend to make heavy demands on people. I don't have time or energy to give much one-on-one, and so I'm very hard on people around me. I take much more than I give. I give to people in the shelter, I give to people on the streets, I give to people who are suffering, but that's got little to do with people who are around me. They pay the price."