The ghost of apartheid past is haunting Prime Minister Pieter W. Botha these days.

"Let a black man be trained as an airplane mechanic, let him overhaul a Boeing 747 from nose to tail and let P.W. Botha and his Cabinet go for a ride in it," taunts Jaap Marais.

The challenge is not meant to be taken literally; it is Marais' way of berating the man he says is "selling out" whites in South Africa. As Botha tries to modify apartheid without endangering white power, Marais believes his remarks are falling on fertile ground.

Rank-and-file Afrikaners who form the bulk of Botha's National Party supporters used to hear their leaders tell them that apartheid-as-it-was is now and always will be. So Botha's message that the contribution of blacks and Coloreds (the government's designation for persons of mixed race) to the economy and defense effort must be recognized, and his moves to legalize black trade unions and relax the color bar in jobs and some public facilities, is all a bit unnerving to his followers, Marais maintains.

Marais has been waiting in the wings for 11 years for this. In 1969, alarmed by government moves to allow some integration in sports and fearing that those concessions would lead to others, Marais helped found the Herstigte Nasionale Party, or Reconstituted National Party.

As a result, he became a political outcast, losing the seat in Parliament he had held for 11 years as a National Party member. He was charged with violating the country's Official Secrets Act for reading an internal police memo in public, and was thrown out of the secret society of Afrikaner men, the Broederbond. He believes the police still bug his telephone.

But now enter Marais, far right.

"Stay white my people," reads the slogan draped across the stage. Outside, posters show a white family of four spread over the map of South Africa with the heading "this land is our land." Of late, hundreds of Afrikaners, young and old, have come to see this diffident, almost shy man become a fiery, long-winded orator on stage, where he "tells it like it is," according to his supporters.

"We have the biggest kaffir-boetie [black-loving] government ever," Marais said. He calls Botha to task for his policy of "concessions and appeasement" that is leading to black majority rule and to "the same disastrous path" that was followed in Zambia, Kenya and Zimbabwe.

More than 190,000 white voters bought Marais' politics in South Africa's white elections April 29. "Afrikaner unity in the political sense of the word exists no longer," wrote the Afrikaans-language Sunday newspaper Rapport, noting that 33 percent of the Afrikaner voters defected to the Herstigtes and another tiny right-wing party.

The Herstigtes did not get a seat in Parliament, but this backlash could send troublesome repercussions into Botha's party if Marais' analysis proves correct.

"You must realize," Marais said in an interview, "that there are now 22 members of Parliament whose majorities range from 400 to 2,200 votes. Those are all marginal seats now and they know that this was the last election in which they could win those seats. This has the psychological effect, that in order to protect their own interests, they must show resistance against Mr. Botha."

"We have always had the situation that when a government starts losing support, it follows an inevitable course," Marais said. "It cannot regain its former strength and Botha knows this. I don't have much respect for his intellect otherwise, but he knows this."

While Pauline, a young black servant, served tea, Marais sat on his living room sofa scattered with hand-crocheted pillows, his daughter's cello in a corner, and explained how he felt about apartheid.

"It is a situation which has all the wisdom of observation and intuition that our forefathers had. Seemingly insignificant things in relationships between black and white in South Africa form part of a social fabric which cannot be disturbed at one end without affecting the whole and that is the problem with this government's policy of concessions," said the man who was born 59 years ago on a farm in Cape Province and worked as an Afrikaans-English translator before going to Parliament.

"In the past, the people had the inclination that the government was doing more for the blacks at the cost of the whites, but they didn't seem to have the evidence. Now, they see blacks coming into the towns in big numbers, cramming into the shops," Marais said.

The Herstigtes want all blacks to live in the 10 black reserves or homelands, where they would eat, sleep and vote, traveling to "white" South Africa only to work.

This is an old vision of apartheid, but the Herstigte party platform says it has never really been tried. They call for development of the homelands, which comprise less than 20 percent of South Africa, though "economic decentralization and labor-intensive schemes of afforestation, irrigation and road-building."

Their platform also demands that South Africa pull out of the United Nations, stop sending food supplies to neighboring black states supporting anti-South African "terrorists" and establish a territory for South Africa's 2 million persons of mixed race. They want Afikaans to be the only official language of South Africa, and at their last congress they slammed the government-run television for "bringing blacks into our living room."

For Marais there is no other way. "Even if you switch it around and gave 80 percent [of South Africa] to the blacks and 20 percent to the whites, it is not going to make a difference.Blacks in Africa and South Africa have not shown an ability to provide economic development at the rate they require to provide jobs for their offspring. Look at Zaire, Malawi and Mozambique, where they have the whole country, even then they cannot provide the jobs," he said.

"Our contention is that whatever policy you follow in South Africa . . . there is one absolute imperative," Marais continued. "The whites must form the core.

"We quite accept that there is a large black population who contend they are part of South Africa and should be treated on an equal basis with whites.

"But once you concede that, then you must be prepared to concede that they will be a majority and it would end in a one-man-one-vote system. This would be the end of all stability and progress in South Africa. It would be the end of the white nation in South Africa.

"As far as the Afrikaners are concerned, my forebearers fought two wars of independence for this country and we are not prepared to concede that we have lost this country, that we will lose this country in a sort of bloodless coup."

Though some of Marais' views often make Botha look positively liberal, some observers say the difference between the two is not that great; that Botha merely gift-wraps what Marais packages in cellophane.

But Botha has affirmed he is going to push ahead with his reformist plans and his party has just put out a publication saying that greater support for the Herstigtes would be a good thing if it meant that "racist" elements were drawn away from the National Party. The battle lines between the two parties will shape up more clearly now as Botha moves to exorcise his ghost.