SOUTH AFRICA'S "Muldergate" is a scandal with a difference. It threatens to do more than bring down the government and shake the moral authority of the ruling class. It may also bring to power just about the most regressive faction of the Afrikaner establishment. Meanwhile, it is generating new pressures to reduce the substantial amount of press freedom still left in South Africa.

The outlines of Muldergate, so named after one of the figures disgrace by it, are clear enough. Believeing South Africa's pariah status to result not from its own regime of legalized racism but from hostile propaganda, the government set out a few years ago to create a multi-million-dollar secret propaganda and influence-buying network. It was to work within the more liberal English-speaking community of white South Africa, and within Western (including American) circles supposedly receptive to appeals for comradeship in capitalist progress, anti-communism and - by inference - the welfare of whites. But thanks to conscientious jurists and journalists, word of the program finally broke. The highest political leaders have been touched, and the government, tugged both to disclose and to cover up, may fall.

Foes of apartheid can hardly lament Pretoria's embarrassment. In a democracy such as whites have so far preserved for themselves in South Africa, scandal takes a political toll. Yet the current government of P.W. Botha holds about as much potential for racial enlightenment as the Afrikaner political context may now allow. If in ranks-closing reaction the Afrikaners turn to their racial and political reactionaries, as they well may, the cost of Muldergate becomes very high indeed.

The other day the government proposed making it a criminal offense, punishable by a $12,000 fine or five years' imprisonment, to publish "any untrue matter" about the police "without having reasonable grounds for believing that the statement is true." The burden of proof would rest upon the asscused. This is a monstrous proposal: In a country in which the police are the ultimate means by which whites rule blacks, it would free the police from effective public scrutiny. A law like this, in the hands of a government bent on showing that Botha-type liberaltiy doesn't pay, would transform Muldergate from scandal to a tragedy.