SOUTH Africa's white minority government keeps trying to subvert the forces of majority nationalism. Gatshagate, the latest scandal in a series of official blunders, could even destroy President Frederik de Klerk's credibility and make the end game of apartheid more, rather than less, prolonged and painful.Knowledgeable locals had long guessed that Zulu Chief Gatsha Mangosuthu Buthelezi's Inkatha Freedom Party was being assisted covertly by the military and the police. But only a few cynics supposed that President De Klerk's government had funded Inkatha's rallies directly and had also bankrolled a Zulu anti-nationalist trade union. In the late 1970s Prime Minister B. Johannes Vorster's seemingly impregnable government was brought down by the Muldergate or Infogate scandal. His government was caught bankrolling a secret global disinformation campaign and spending money lavishly without parliamentary approval. Connie Mulder was then Minister of Information. In the 1980s President Pieter W. Botha doubtless knew that the military's intelligence unit was covertly backing the Renamo guerrilla movement in Mozambique, despite official denials, and also engaging (again despite umpteen denials) in subversion in Angola and Namibia (not to mention Zambia, Zimbabwe, and elsewhere in Africa). Destabilization was the name of the South African game. De Klerk appeared cut from very different moral and political cloth. Nelson Mandela, president of the ANC, and President Bush both believed in his credibility. But Gatshagate has destroyed much of that trust. The latest revelations of double dealing ought to eliminate Inkatha and Chief Buthelezi as prime bargaining partners, contrary to the white government's aim. The party and the chief will now be seen for the puffed up pretenders that the ANC has always claimed they were. De Klerk will have to battle hard to claim continued credibility for his own role as a well-meaning broker of peace. His demotion of Defense Minister Magnus Malan and Law and Order Minister Adriaan Vlok was a first step - but only a first step. Meanwhile, the disclosures about governmental subversion will embolden hardliners and Marxists in the ANC leadership. If De Klerk and his cabinet cannot be trusted to deal squarely with the ANC, then can Mr. Mandela be trusted to lead? This will surely be among the questions that former exiles like Chris Hani will ask. So may Cyril Ramaphosa, the newly elected secretary-general of the ANC. He also leads the largest and most militant black trade union. The ANC itself emerges out of the events of July much stronger than Inkatha, but weaker in that its recent public bargaining postures have largely been based on cooperation with and a belief in the positive intentions of President De Klerk. Gatshagate also shows that De Klerk has sought to hedge against real majority rule much more than his public statements, and his denials since the scandal broke, would imply. Since at least the 1970s, South Africa has tried to follow a two-track policy in bargaining with opponents, Westerners, and nationalists: While professing to compromise, it has disinformed, subverted, and tried to outwit. Then, when the government has been found out, it has tried to wriggle and shake. President Bush's removal of United States sanctions was premature, for the South African government had clearly not been negotiating in good faith, as Congress mandated in 1986. Those sanctions cannot easily be restored, but Washington can keep pressing Pretoria to bargain soon and generously with the ANC. Now that white South Africa's official credibility is at a low ebb, the time has come for De Klerk to work ever more closely with Mandela and the ANC leadership, while distancing himself from Chief Buthelezi.