If Americans don't vote ...

In America about half the potential voters don't bother to vote and the percentage of those who do vote has been dropping. Nobody adequately explains this apathy, which puts America below the voting record of other democracies. The trend may continue. It is one of democracy's most disturbing phenomenons.

Nonvoters next month will be important politically; the turnout percentage in many areas will decide the result. According to the Statistical Abstract of the United States, the voting records for the last five presidential elections follow: 1964 - 69.3 percent; 1968 - 67.8 percent; 1972 - 63 percent; 1976 - 59.2 percent; and 1980 the same as 1976 - 59.2 percent. In short, the percentage voting has dropped by about 10 points in 16 years. Apathy has grown sharply.

It raises political problems. Says Graham Allison, dean of the Kennedy School of Government, ''The government derives its just powers from the consent of the governed; if half the people don't vote, where does authority come from to make choices about foreign and domestic policy, about sending marines to Lebanon or restructuring taxes?''

How long will the peculiar American disassociation from government go on? Is the American system working? For much of the past week Congress has simply been trying to adjourn; it reached deadlock. The budget is unbalanced to an extraordinary degree. The country is living beyond its means. Can this course be followed? If not, and if hardships, unemployment, and inflation follow, there will be very difficult times ahead for either Ronald Reagan or Walter Mondale in the next four years.

There is one school of thought that thinks there is too much room for deadlock and stalemate in the unique separation of powers in America's government. Veteran political scientist James MacGregor Burns has developed this theme. In his latest book, ''The Crisis of American Leadership,'' he charges that ''among the general public distrust in government and lack of confidence in leadership have escalated in the last quarter century, and not only since Watergate and Vietnam; hence there is a mass potential for change.''

Still, he asks, ''Can we depend on the voters to respond?'' They will, he thinks, if the new leaders ''are bold enough.'' The thought is of interest just before a national election. ''It is hard to believe,'' Professor Burns continues , ''that we cannot find among a nation of 235 million embracing a rich profusion of talents, the kind of transforming leadership'' that he argues is required.

Is it the fault of the voters or is it the lack of clearly articulated political parties and an uncomplicated legislative system that dilutes American response? Columnist Flora Lewis writing from Paris contrasts the percentage of European voters who go to the polls, ranging upward from Britain's 72.7 percent.

''The American system,'' says Professor Burns in one of his studies, ''in its ultimate foundation is built upon a belief in weak government.''

Perhaps that accounts for it all. The American election after months of hesitation is finally roaring to its climax. Fine. There is a great deal of excitement in the newspapers and in the air. When it is all over, will the percentage of actual voting be up or down?

(Grandfather Benj. F. Lang, referred to in this space last week, served in the New Hampshire legislature in 1867 under Andrew Johnson, not ''Andrew Jackson ,'' as stated. He would be surprised.)