IT IS amazing when people are amazed over how fast the mighty can be cut low and the lowly exalted in the world of Washington politics. It happens all the time, as Walter F. Mondale and Sen. Gary W. Hart (D-Colo.) are proving right now.

But even in the rarified atmosphere of Capital Hill reputation mongering, the most jaded cynic can't help but be bemused over the rollercoaster ride the reputations of three so-called giants of national security policy have taken over the past decade. The melodrama of Cap and George and Henry the K--reaching one of its most interesting chapters in recent months--goes to show once again just how transitory stature in Washington can be, how fleeting prevailing wisdom really is, and, perhaps most fascinating, how little general smarts, can matter in foreign and defense policy.

You remember, of course, Casper W. Weinberger '38 and George Shultz. They first made it big in the halcyon days of the Nixon White House Cap was "Cap the Knife," Nixon's "chief executor of sacred cows," in Newsweek's words. A fiscal conservative, but a Rockefeller liberal, they said, a man who took the surgeon's knife to the vast bureaucracy at the Federal Trade Commission, then the Office of Management and Budget, and finally the Department of Health, Education, and Welfare. "He's no ideologue," said one liberal congressman when Weinberger was named Defense Secretary three years ago. "He was one of the people who made things work." "He was the man who would sculpt the Pentagon into a mean, but lean, fighting force.

This is exactly the same image that had been cultivated by George Shultz up until his appointment to succeed Alexander M. Haig as Secretary of State Shultz was the giant of domestic policy in the Nixon Administration--"a careful listener, a former academic who has become, in the estimate of his friends in government and business, a master manager with an uncanny knack for getting the best of people," said Newsweek. His resume was as impressive if not more so than Weinbergers': Secretary of Labor, head of the Office of Management Budget, and Secretary of the Treasury, where he negotiated a trade agreement with the Russians, making influential friends in European capitals along the way.

Two obviously smart guys. Two similar guys, not only do their resumes sound the same, they both worked for the engineering behemoth Bechtel, when they weren't stomping in and out of the Oval Office.

BUT in the fast paced elevator that is Washington, their fall from grace has been swift and severe. And just as quickly, another fallen star, Henry A. Kissinger '50, may rise again.

Weinberger is the easiest to pick at, because, by most accounts, he is one of the worst defense secretaries ever. He is not stupid, nor have his policy proposals, in their own may, been insignificant. By pressuring unremmittingly for a huge arms build-up, he has redefined the debate on defense spending. The question is no longer do we have increases of a few percent in the budget; it is do we increase it by more than 10 percent or not.

But it is his very inflexibility on the Pentagon budget that reveals the heart of the Weinberger problem. A fascinating article in the National Journal on Weinberger describes how, in the wrangle over the '84 budget, Cap could have struck a deal with congressman for a seven percent real spending increase, but had to settle for five because he refused to compromise. Even in off-the-record discussions, the article went on to say, Weinberger refuses to recycle anything more than standard Pentagon positions on issues.

In essence, the man is a stonewaller. It is Weinberger--and his adviser on these issues, former Henry Jackson aide Richard N. Perle--who has quashed even the sightest mention of arms control in the Administration. It was under his stewardship that the oft-noted Pentagon prediliction for waste has blossomed into a near crisis. Weapons systems costs are consistently under-budgeted and the procurement process is consistently under fire for over-inflated prices Weinberger's rigidly ideological approach to defense issues has cost him his credibility, and when he speaks, no one listens.

SHUTLZ'S fall from grace has been much less obvious or dramatic, but in many ways much more interesting. After all, Weinberger, for all his supposed bureaucratic skills, was still known, was skill known as a hard-liner on defense. But Shultz was real giant-killer, the man waiting in the wings all during Haig's failed vicarship, ready to restore cool, business-like leadership to an aggressive U.S. foreign policy.

They're not saying that anymore, though, as Giant George is on the ropes, fighting to last another round. His stumbling block this last year has been Lebanon, a morass by any measure. Can you imagine what the second guessers would have done if Jimmy Carter and Cy Vance pursued the policy undertaken by Reagan and Shultz? Equivocate over whether they like the Israeli invasion or not. Refuse for a year to acknowledge that Syria has any interests whatsoever in the country. Send in several hundred marines without a clear idea of what they're doing and get more than 200 of them killed doing it. And then watch as Syria eats up the country. Even though Reagan doesn't admit it, the emperor has no clothes, and the people are beginning to know it.

A lot of the blame for the Lebanon fiasco lies with Shultz. People think that he never fully understood how far the Syrians were willing to go to get their way. Shultz never showed the requisite leadership to stop the steamroll of events, and, in that sense, deserves to be faulted for the loss of the U.S.'s strategic and moral stature. Now, as the first faint cries for his resignation are heard, the heretofore "cool teamplayer" is starting to flail at Congress on Central American policy. A drum beat of Foggy Bottom corridor criticism of the secretary is starting to creep into the papers. This guy may not be so cool after all.

THERE seems some kind of lesson in Shultz and Weinberger's fall from grace. The man some people think is going to be the next secretary of state--if Reagan makes it to the Oval Office again--is Kissinger, another refugee from the Nixon White House. He has been called the greatest diplomat in the world, but he earned that title at a terrible human and ethical cost, as journalists like William Shawcross and Seymour Hersh have shown in recent years. Kissinger is everything Shultz and Weinberger are not. Where the later are bureaucratically clumsy, the former is manipulative. Where Winberger and Shultz have their integrity intact, Kissinger is called unscrupulous.

Yet, as Weinberger and Shultz fall, Kissinger rises like the Phoenix. The Central America Commission leadership is only one manifestation of the rescusitation of his reputation; Kissinger reportedly sees Shultz and Reagan regularly. It is Kissinger, the scoundrel, who may carry on the Nixon banner, not Shultz or Weinberger, two men of integrity. Sy Hersh's darts were sharp indeed, but not sharp enough. They don't matter anymore The American people value competence, and it looks like Cap and George don't measure up.