Practically nobody has anything good to say about America's system of divided government. Yet somehow it works - and often very well. After World War II, when some 100 new governments were set up around the world, not one imitated the American form of divided government. Yet the United States Constitution, soon to round out its first 200 years, is still going strong. In a year from now, on Nov. 6, 1984, it will hold its 50th presidential election. Its government is still divided into three branches - executive, judicial, and legislative - warily eyeing one another. Students of politics watch in fascination, and often complain they don't know who is in charge. But the system goes on just the same.
Once more the cycle repeats itself. Around the nation today candidates are saying how critical the situation is - nationally and internationally - and urging citizens to gird for decision. Yet if past trends continue, when the ballots are cast in 1984, only about half those eligible will vote.
The percentage has been going down like a flight of stairs for five elections. In 1964, 61.7 percent voted; in 1980 that percentage had shrunk to 53 .95. And still fewer Americans vote at midterm. Few nonpresidential races seem to excite much interest. Only 45.9 percent voted in congressional elections in 1978. In 1982 it was 48.5 percent.
''Two-thirds of our people do not even vote,'' President Carter said in July 1979. ''A crisis of confidence . . . threatened to destroy the social and political fabric of America,'' he warned then. The public did not heed. Voters were in a sour mood with the failed attempt to rescue the Iranian hostages, and they defeated Mr. Carter in 1980. And the election turnout, 53.95 percent, did not increase. In other democracies, normal voter turnout is 70 to 80 percent or higher.
James L. Sundquist, a scholar at the Brookings Institution, a private research organization, offers a typical comment. Yes, he says, occasionally the American system works brilliantly, separated executive and congressional establishments collaborate, the gears mesh. But often the divided elements ''will not be welded together, and the whole clumsy apparatus of the national government will continue, as it always has, to function in fits and starts, with more deadlock than dynamism, more drift than distraction.''
The old dilemma of the separation of powers remains unresolved and to a large extent insoluble. To that extent, the crisis of competence is endemic to the American government. The republic will survive, but its effective functioning, year in and year out, cannot be counted on. And nothing much can be done about it.''
Overly pessimistic? The strongest support of all for the system comes from the record of the country's achievements. Pride and enthusiasm take an inspirational form in surveying two centuries of American history.
Yet there is an undercurrent of anxiety that finds occasional expression at national election time. Is the process too long? It is noted that British elections last only five weeks (where an average 72 percent vote). Some of the 1984 presidential candidates have already been running for two years.
There is a question, too, about the selection of candidates. A hundred years ago Britain's ambassador to the United States, James Bryce, in ''The American Commonwealth'' argued that America did not choose its best citizens for president: The system was weighted in favor of the most electable candidate, not the ablest, he said. And recently this argument has been heard again and again.
Are we getting the best? No president has served two full terms since Eisenhower. Opinion polls report that since the mid-'60s Americans have suffered a sharp loss of confidence in their institutions. The ''index of alienation'' from pollster Louis Harris, and that of the Center for Political Studies at the University of Michigan, disclose a steep slide in popular regard for Congress, for the executive branch, and for nongovernmental institutions.
There has been unemployment, inflation, and uncertainty recently. Many Americans wonder why the country can't balance its budget. Criticism comes from high sources.
Ronald Reagan in a fit of exasperation (in May 1982) declared that ''nothing in our federal government is more in need of an overhaul than a ridiculous procedure we have misnamed the budget process.'' He called the process ''the most irresponsible Mickey Mouse arrangement that any government body ever practiced!''
In establishing the US, the Founding Fathers deliberately planned a weak central government. Their contemporary world was being run by kings, czars, and emperors, and the bold new republic was designed to be something different: The Constitution was the answer to England's King George III. Today after 200 years it is not unpatriotic to note that parts of the American governmental system are criticized, sometimes sharply. Prof. James MacGregor Burns charges that ''deadlock and drift are the normal state of governmental affairs in this country . . . broken only occasionally by bursts of creativity.''
Or again, Lloyd M. Cutler, a former counsel to President Carter, writing in the quarterly Foreign Affairs (fall 1980) said the system often brings unjust criticism of the chief executive (as it may again in 1985 when a new administration, whether Republican or Democrat, takes over): ''The public and the press still expect presidents to govern. But the president cannot achieve his overall program and the public cannot fairly blame the president, because he does not have the power to legislate and execute his program.''
Two centuries ago the authors of a then-new Constitution appealed for its acceptance, using the argument that the document carried provisions for correction if difficulties developed. Thomas Jefferson said he thought there should be a constitutional convention every generation. He said: ''Laws and institutions must go hand in hand with the progress of the human mind. . . . We might as well require a man to wear still the coat that fitted as a boy, as a civilized society to remain ever under the regimen of their barbarous ancestors.''
Alexander Hamilton wound up the 85th (and final) issue of the Federalist Papers with the argument that the Constitution could be amended later: ''It will be far more easy to obtain subsequent than previous amendments to the Constitution,'' he said. He looked forward to ratification ''with trembling anxiety,'' he added.
So now in 1983 the rivals for the White House once again are considering the rules of the game as they debate the issues. It has been less easy to amend the Constitution than appeared at first, and Jefferson's idea of periodic constitutional revision has been disregarded. I asked Dumas Malone, the great Jeffersonian biographer and historian, about this: It was at the Miller Center of Public Affairs at the University of Virginia. I cited recent criticism of the separation of powers:
''I share your great concern about the state of our political mechanism. I think it's terrible,'' Mr. Malone said. ''I think we are ripe for a constitutional convention. . . .'' Then he continued abruptly, ''But nothing would terrify me more.''
''Would you vote for it, or against it?''
''I think I would vote for it, but I would be scared . . . and I wouldn't know what in the world would happen to it after they got through. If they did what they ought to do, I don't know whether the public would accept it or not, so I'm awfully depressed about the possibility.''
The doubt lingers in many minds. Now the United States is undertaking another of its quadrennial elections, and criticism of the process rumbles anew. It is too long, too uncertain, critics say.
This year the campaign comes at a time of extraordinary strain at home and throughout the world. Washington's budget woes continue, and a series of $200 billion deficits could stretch ahead. The US no longer has its former military and economic predominance abroad, and the nuclear threat persists.
At home, voter participation has declined, and there are questions about the system itself. Who runs the government in Washington? For about half the time since World War II, the political party controlling the White House has lacked control of one or both houses of Congress.
Occasional pessimism with the system is nothing new in America's extraordinary success story. ''Democracy never lasts,'' John Adams said gloomily two centuries ago. ''It soon wastes, exhausts, and murders itself. There never was a democracy yet that did not commit suicide.'' The incorrigibly combative Adams would have been delighted (and perhaps astonished) by the failure of his prophecy.
At times the American governmental system has worked brilliantly. Often this happens when a particular set of conditions is met after a presidential election. One example occurred during the first two years of Woodrow Wilson's presidency. It was labeled the ''New Freedom.''
Another happened in Franklin Roosevelt's first term - ''the New Deal.'' A third was the early ''Great Society'' period of Lyndon Johnson. In each case emergency conditions had built up with a blockage of action and a growth of voter emotion. Then came an election mandate and a sudden release. In the case of Woodrow Wilson, he reformed tariffs, business, and banking and set up the Federal Reserve System: ''I summon all honest men, all patriotic, all forward-looking men, to my side,'' he declared.
Congress and the public responded as it also did for Roosevelt and during the first years of Lyndon Johnson. It would seem that a special set of circumstances must prevail. There must be a conspicuous need, and a strong unified force in Congress that responds to a vigorous leader.
Are such conditions present today? Some feel that in recent years there has been a decline in governmental effectiveness, a falling-off in presidential control, and a disintegration of political parties. There has certainly been a drop in voter participation. Must elections be so long? wonders much of the public. Many read it as a sporting event that occurs every four years in the fall after the World Series.
Less and less do political parties indulge in ideological campaigning and more and more do candidates organize their camps independently, sometimes marketed on TV by advertising specialists. Presidents Carter and Reagan, it is recalled, each came to Washington by ''running against Washington.'' Once more America goes through its unique election process. There is grumbling, but the system works.