Johannesburg — The South African government has a new case of right-wing jitters. And it is putting the tentative ''power-sharing'' plan of Prime Minister Pieter W. Botha in jeopardy. Earlier this year it appeared that the plan was set for implementation, but now it must jump through more hoops. The outcome at this stage remains unpredictable.
Prime Minister Botha has decided to test support for his ''reform'' plan among the groups it encompasses. Whites are to vote in a referendum at a time not yet set. Coloreds (persons of mixed-race descent) and Indians will be allowed to express their opinions in a manner to be negotiated with the ''leaders of those communities,'' according to Botha. The ''power-sharing'' plan excludes the black majority, which therefore will not be included in any poll.
The prime minister is searching for a mandate, say political analysts, partly out of concern about the outcome of two highly symbolic by-elections next month in conservative Afrikaner strongholds.
But although fear of a right-wing defeat in those by-elections prompted the referendum decision, it also has pushed the government to the right as it battles for ultraconservative white support. That is sowing new doubt about Botha's reform initiative, particularly among Coloreds and Indians who might support the government in a future opinion poll.
The ambiguous nature of the power-sharing reform plan is one reason the government's support to both the right and the left is so tentative. The plan calls for bringing Coloreds and Indians, but not blacks, into a new minority government where whites would still retain control.
The endless debate here: Is the plan the first step toward real reform that would include the black majority? Or is it the final closing of the door on black political aspirations?
Prime Minister Botha has remained vague, letting white voters see whatever they want in the power-sharing proposal. In so doing he has contained right-wing defections, which peaked last year when Dr. Andries Treurnicht split from the National Party and formed the Conservative Party, claiming the reform plan violated white privilege. Botha has at the same time gained some support on the left from pro-reformists who feel the reform initiative, though inadequate, is the only game in town.
In campaigning for the two May 10 by-elections in the northern Transvaal Province, the ruling National Party has so far catered to right-wing sentiment. Government ministers have used emotive apartheid terminology, with the leader of the Transvaal, F. W. De Klerk, insisting in Parliament that the National Party has been ''following one straight course since 1948 until today. . . .''
Much is at stake in the by-elections. Dr. Treurnicht is up for reelection in the Waterberg constituency, and Nationalist Minister of Manpower S. P. ''Fanie'' Botha, who has brought progressive change in South Africa's labor laws, is being challenged in Soutpansberg. Defeat of either one of them would be a big blow to their respective parties.