"The system of apartheid means deliberate, systematic, institutionalized racial discrimination denying the black majority their God-given rights. America's view of apartheid is simple and straightforward: We believe it is wrong. We condemn it. And we are united in hoping for the day when apartheid will be no more."

PRETTY GOOD STUFF, right? We thought so. President Reagan said it yesterday in proposing to decree by executive order most of the sanctions that veto-proof majorities in both houses were prepared to legislate against South Africa. The Republican-controlled Senate promptly sidetracked the legislation. Leaders in the Democratic-controlled House sharply berated the president and his plan.

Mr. Reagan's critics need to look carefully at what has happned. For it appears that the president has, finally, come to a public view of apartheid that reflects the intense and instinctive dislike that most Americans feel. His past statements have often read like defenses of apartheid, and have engendered a widespread distrust of his "constructive engagement" policy. Yesterday, however, Mr. Reagan had it right -- facts and tone. If he can stay on that track, his can become a voice other Americans will be pleased to have speak for them.

Some of Mr. Reagan's critics profess to find his new position full of loopholes and devious relief for the Pretoria regime. They would do better to focus on holding the president to the new terms he has embraced. Otherwise they stand to be accused of being prepared to snatch defeat from the jaws of victory for strictly partisan gain.

It was always clear that the person most open to influence by Congress was not P. W. Botha but Ronald Reagan. Now Congress has done it. It has changed his voice and gotten him to embrace most of the specific sanctions in the legislation. It has brought the president into a respectable national consensus on an issue of great political and moral moment. Why would responsible anti-apartheid people want to advertise the remaining relatively small differences on sanctions and thereby convey to Pretoria the impression that there is comfort for apartheid in the space between?

In the face of the new political context created by the president's switch, the House must now in effect start all over again to legislate, if it goes that route. In these circumstances, it seems to us reckless to undertake to bring along another bill that would still face a reluctant Senate and that in any event could go only marginally beyond the president's executive order.

The Reagan sanctions do not cut deep into the South African economy: they scarcely could and still respect the general wish to jolt apartheid but not to harm its black victims. Certainly these sanctiot cut nearly as deep as the actions that private American banks undertook recently to protect themselves in South African seas turned ever stormier by domestic protests. But the sanctions do cast a long political and psychological shadow on South Africa's rulers, who despite their disclaimers register with infinite sensitivity what others -- and most of all Americans -- think of them. The sanctions can cast such a shadow, anyway, if Democrats will allow them to.