Kennedy was shot. Johnson, after a brilliant season of legislative achievement, chose to abdicate when he was so unpopular over the Vietnam War that he could hardly leave the White House except to visit military bases. Nixon had his moments of glory in detente with the Soviet Union and the opening to China, then was forced to resign.
Ford, Carter, and Bush were all defeated after a single term. Ronald Reagan was successful for five years. Greeted by most foreigners as a buffoon or the next thing to it, he changed the political climate at home and put so much pressure on the Soviet Union that it shook to pieces. He was more beloved than any president of modern times. But he was lucky not to impeached over the sinister farce of the Iran-Contra affair.
And now poor Bill Clinton is facing disaster in the most painful and humiliating way - after six years when he has presided over unprecedented prosperity, conducted foreign affairs with decency and imagination, but utterly failed to make his mark on a Congress tightly controlled by his conservative enemies.
On the face of it there might seem to be little connection between these sad stories, little institutional rhyme or reason behind them. On a closer look, however, there are a number of common themes which add up to a question of great importance not only to America but to the world. The presidency may be the most powerful office on earth. But how well does it work?
The presidency is powerful, first of all, because the United States is powerful. A president can order Tomahawk cruise missiles to come through my window. That does not mean he can do what he wants, or even much of what he was elected to do. Within the American system - and few foreigners fully understand this - he is not only not all-powerful, he is not very strong at all.
Forty years ago it was fashionable for academic students of the presidency like Richard Neustadt to point out how weak it was. The power of the presidency, Neustadt said, is only the power to persuade. But those advocates of an imperial presidency were liberals. They were nostalgic for the masterful ways of Roosevelt, and they regretted the passive way in which the office was operated by an ageing and invalid Eisenhower. They said the presidency was weak because they wanted a liberal like Kennedy to make it strong.
A hundred years ago, however, Woodrow Wilson, later himself an activist president after he finished writing books about politics, judged that the American constitution was one of "congressional supremacy". The power of the presidency, in other words, grew, and now has receded again.
The United States lives under a constitution elaborated in the 18th century according to a strict theoretical separation of powers between executive, legislature and courts; since then, effective power has swayed to and fro in long cycles between the Congress and the President.
Under Wilson in the First World War and Franklin Roosevelt in the second, and under Truman, Kennedy and Johnson in the Cold War, circumstances at home and abroad - in a world of political, economic and military crisis - demanded a strong presidency. The unpopular Vietnam War saw Congress begin to assert its rights again. Since the fall of Communism, the Congress - largely unnoticed in Europe - has reimposed its supremacy.
The president can bomb Sudan or Afghanistan. But he is powerless to persuade the Congress to go along with his ideas on health reform or even to contribute to the United Nations or the IMF. Because it is the president we see waving from the top of airport steps, or touring Russia or Ireland, we make the mistake of thinking he is the emperor of the West. He is not even the emperor of both ends of Pennsylvania Avenue. There are 537 emperors in Washington: 100 in the Senate, 437 in the House, and only one in the White House.
If, and it is a very big if at the moment, the Democrats could capture even one house of Congress, so that a future Democratic president would have some chance of passing his legislation, then things might change. If, and it is more plausible at the present, a Republican wins in the Millennium presidential election, then, too, things might change. But for now, even a president who was not desperately fighting to hold on to his job would have little power.
The expectation remains. But the substance has departed. For the time being, with the economy booming, unemployment low and stock market still high by any but its own recent standards, not to mention a great baseball season, it does not strike many Americans that it matters.
Even if they were to come to feel they needed strong leadership, it is not likely that the constitutional pattern would change. The constitution is bedded in custom, institutional practice and near-religious awe.
Yet when one presidency after another ends in frustration or disaster, it is not surely logical to ascribe institutional malfunction to individual person- ality defects. The presidency doesn't work, not because Nixon or Clinton were bad men, but because Americans expect too much of their presidents, and give them too little authority to meet those expectations. That is why the problem of the presidency will remain.
t Godfrey Hodgson is a Fellow of Green College, Oxford. He is the author of `All Things to All Men, the False Promise of the American Presidency'.