If American voters are as apathetic as they are believed to be, the percentage of those going to the polls Nov. 4 may be a record low. The situation may change, but a scornful electorate keeps telling pollsters that it sees little choice between the major presidential candidates and is indifferent to the outcome.

The notion that nothing significant is at stake this year is a myopic view, for a lot more is riding on the election than the campaigning of Jimmy Carter and Ronald Reagan may suggest. Actually, the voters have a clearer choice this year than in recent election, as a glance back at the tame 1976 Carter-Force race amply demonstrates.

Of all the things that endanger the world, none surpasses the threat of nuclear war. Four years ago, both presidential candidates supported the limitation of strategic weapons as embodied in the proposed SALT II. Today, however, Carter and Reagan could hardly be farther apart on this crucial issue.

A few days ago, the president sent Secretary of State Edmund Muskie to the United Nations to inform the world, especially the Soviets, that the Carter administration is not only ready but eager to "move forward as speedily as possible toward ratificationof the SALT II treaty." Muskie indicated it would be the first order of business if Carter is reelected.

Reagan, on the other hand, is not only opposed to SALT II, but both he and the Republican platform are committed to achieving "superiority" over the Soviet Union, a policy that obviously invites a no-holds-barred arms race, regardless of the cost or the end result.

Carter's arms control program, like Richard Nixon's and Gerald Ford's, remains based on parity. In 1976, there were no marked differences between Carter and Ford on this critical issue, nor on the question of detente with Moscow, a policy that Ford inherited from Nixon and that Carter did not challenge.

As for military expenditures, both Nixon and Ford cut the defense budget. In the 1976 presidential primary campaign, Reagan accused Ford and then secretary of state Henry Kissinger of letting the United States become No. 2 militarily. Carter, however, wanted to trim the Pentagon budget even more, so there was no arms buildup controversy in the 1976 campaign.

Four years ago, there was little difference between the Democratic and Republican candidates on the emotional domestic issues that so sharply divided Carter and Reagan, particularly abortion and the Equal Rights Amendment.

In 1976, the Republican platform, as well as the Democratic one, unequivocally backed ERA. This year, the GOP and its nominee are opposing the amendment. Carter strongly supports the ERA, and has promised to continue seeking its ratification if reelected. t

In the Carter-Ford campaign, the question of abortion and the proposed constitutional amendment the outlaw it did not figure in the election, but it has become one of the most inflammatory issues in the Carter-Reagan contest.

Neither nominee is for abortion personally, but what matters is that Reagan favors the amendment to ban it and Carter doesn't. They also differ on introducing prayer in the public schools, with Reagan for it and Carter supporting the Supreme Court's decision forbidding it. Like ERA and abortion, school prayer has never before been a conspicuous factor in a presidential election.

For voters who are concerned about the future of the U.S. Supreme Court and other federal tribunals, the coming election also provides a choice, since it is clear that the rival candidates have a different criteria for selecting justices.

Even Carter's severest critics concede that his judicial appointments have been exemplary, with the emphasis on integrity and excellence. There is every reason to assume that he would apply the same high standard in filling future vacancies on the nation's highest court.

In contrast, Reagan subscribes to the Republican platform, which for the first time explicitly establishes ideology as a priority in naming federal judges. The platform calls for the appointment of jurists who "respect traditional family values and the sanctity of innocent human life." That, of course, is taken to mean judges who reject abortion.

It is easy to understand the dissatisfaction of millions of voters with both Carter and Reagan, but the candidates at least are not Tweedledum and Tweedledee. There is a distinct difference. There is, this time, a real choice for the electorate.