He came to Washington in 1978 and, by his admission, did not have a dime in his pocket. He hitch-hiked from Gastonia, N.C., without a college degree and got a job sorting mail from 3 a.m. to 8 a.m.

Then he climbed the Republican ladder, taking jobs on Capitol Hill, landing a White House job and now running his own consulting firm representing South Africa for $390,000 a year.

His name is William A. Keyes, he is 32, he is South Africa's newest lobbyist. And he is black.

Only one South Africa lobbyist, John P. Sears, a campaign manager for Ronald Reagan in 1980 who claims access to top administration officials, is paid more by South Africa, at $500,000.

Unlike Sears' chief lobbying target, Keyes' is not the U.S. government. He is taking aim at black Americans who have become the core of this nation's antiapartheid movement. Like the little Dutch boy with his finger in the dike, Keyes' job is to stop a rising tide of black American opposition to the South African government.

His qualifications are his opinions -- supporting the government of President Pieter W. Botha -- and the fact that he is a black American, according to other lobbyists, who note that Keyes is an unknown to black American leaders.

Since signing his contract with South Africa in August, Keyes has arranged meetings between black reporters and Louis Nel, South Africa's deputy minister of foreign affairs. He has also approached black American businessmen about business opportunities in South Africa.

"I find it incredible," said Randall Robinson, head of TransAfrica, the foreign-policy lobbying group leading antiapartheid protests. "It is the kind of thing that is a shock to your system to see a black American lobbying for the South African government. But I guess in the spectrum of human behavior anything is possible. This is clearly very unusual behavior."

Keyes views the antiapartheid movement askance as well, saying, "One-man, one-vote is the principal question only for activists outside South Africa. The principal question to men and women in South Africa is . . . whether they will be able to provide for themselves and their families . . . After they deal with that, political participation comes into play.

"It's troubling to me," he added, discussing American civil rights activists fanning U.S. opposition to the South African government, "that people here in this country pursued a nonviolent course in the struggle to have their civil rights protected and yet will condone violent means in another country . . . It's not only distressing. It's downright hypocritical."

Keyes has made himself available as a counterforce on television to anti-South Africa salvos. He appeared on Cable News Network last month when, in a taped interview, Winnie Mandela, wife of jailed South African dissident Nelson Mandela, had moments earlier described Botha as certain not to dismantle apartheid unless the United States applied "total" sanctions against South Africa.

Bernard Shaw, interviewer on CNN's "International Hour," turned to Keyes in the studio. "What say you to that?" he asked.

Keyes shook his head and said, "It's important that we recognize in the U.S. the reality of the ANC (African National Congress) as a terrorist outlaw organization which has perpetrated violence primarily against innocent black people," said Keyes, describing the organization in which Nelson Mandela was a top leader.

"I don't think very many of us in this country are willing to stand up and say we favor the type of violence perpetrated against black South Africans by the ANC and groups of that kind which are being controlled by communist parties in South Africa and the Soviet Union," he added.

Keyes hitch-hiked here in 1978 and, after the mail-sorting job, took a pay cut for a job as research assistant with a Republican study group.

Then, he climbed the conservative ladder, working first for the Amerie American Conservative Union as a welfare-policy expert. Then he jumped to the Joint Economic Committee of Congress while leading the fight to gain approval of tuition-tax credits in the District. In 1982, he went to the White House as a low-ranking domestic policy adviser.

In two years there, Keyes found himself ignored and treated "shabbily," according to former associates. He told one person that he "hated" his White House colleagues and said he felt that they did not respect him because they saw a "black face."

He quit the White House and tried unsuccessfully to start a black-oriented newspaper here. Then he formed Black PAC, a black Republican political action committee to finance black Republican candidates. The PAC was slow to attract money.

Unemployed for a year, Keyes signed up for a free trip to South Africa from the South Africa Foundation, which pays Americans to take fact-finding tours of South Africa. He met twice with deputy minister of foreign affairs Nel. The second meeting, Keyes recalls, led to a more private, dinner-table discussion of black America's role in the growing U.S. antiapartheid movement.

That was followed by a meeting with Foreign Minister R. F. (Pik) Botha.

A month later, in Washington, Keyes signed his $390,000 contract to act as a lobbyist for South Africa.

Keyes said he has not attracted cat-calls from other blacks. In fact, he said, black businessmen have been calling to ask how they can start business deals with South Africa.

He said that his mother, a Democrat, had questions about her son dealing with a government favoring strict separation of the races and that he managed to reassure her.

Keyes had worked in South Carolina for an unsuccessful congressional candidate but, according to his wife, grew "dissatisfied with Democratic Party politics . . . . He realized he was more comfortable with Republican Party principles."

Keyes said he has no "problem whatsoever so long as I have the opportunity to explain to people what it is that I am doing. One of the first things I do is to remind people that South Africa is not just a political issue but a country that has people in it . . . .

"The question I ask people is 'Does getting arrested out in front of the South African Embassy help solve any of those people's problems, or are there other programs we should put into effect if we really want to benefit those people? . . . .

"I go on to explain to them that my contract with South Africa is different from any other contract that the South African government has entered into with consultants here. My responsibility is simply to work on programs that benefit black South Africans in particular with the indirect benefit accruing to the government and the country at large . . . ," Keyes said.

Keyes said he is more rankled about a New Republic magazine commentary entitled, "Comparable Worth." It said Keyes has a case for comparable worth because he is paid less than Sears to lobby for South Africa.

"They didn't mention the other lobbyists for South Africa who get less than I do," Keyes said. "And in the next few months, when I start representing them on the West Coast, my contract will reach the half-million mark . . . . There is only one other person I have to share my money with . . . . Sears has a whole firm he has to support."