For months, Americans have been confronted with disclosures of scandal in public and private life. Involved are betrayals of trust by institutions and leaders exercising vast power in Wall Street and Washington. Reputations of American colleges are also being damaged by unethical behavior of educational officials, trustees and alumni.

The scandal at Southern Methodist University -- "Ponygate," naturally -- involves the governor of Texas and under-the-table payoffs to football players and is only the latest of many such affairs that mock professed principles of amateur athletics and good sportsmanship.

Taken together, these raise disturbing questions about the nation's ethical climate and the standards it most values. They also are certain to form a major theme for political debate in next year's presidential campaign, even now under way, and for good reason.

Not since the 1920s, a decade that these Teflon Years of the 1980s increasingly resemble, has the nation witnessed so much common celebration of greed and selfishness. Now, as then, the country has been encouraged to follow the example of big-deal operators, get-rich-quick schemers, inside traders, market manipulators, laissez-faire entrepreneurs in political and corporate life. Private gain has been accorded a higher value than public service. "Making it" has been the era's slogan.

Whether this decade ends with a sense of disillusionment similar to that experienced by Americans after the giddy boom of the Twenties turned into historic bust, forcing a painful reexamination of all institutions and national leaders, cannot be determined now. But already, much of the glow of the early 1980s has been dissipated by evidence of major scandals and pervasive mismanagement.

The public has reacted with growing disgust to revelations about secret and duplicitous Iran arms deals, Wall Street fixers and collegiate bagmen. Confidence has been shaken. In turn, this has created a far more receptive public mood for serious discussion about the nation's political direction and ethical standards.

In that respect, one of the announced presidential candidates made a little-noted speech several days ago that could have strong public appeal.

Rep. Richard A. Gephardt (D-Mo.), speaking at the prestigious Securities Industry Institute of the Wharton School of Business, noted that he had been asked to address "economic issues." He was going to do that, he said, but not in the way his listeners might have expected.

"I want to recall our attention to what our economy is really all about: not money, but people," he said. "The original Greek word 'economy' meant 'the management of a household or family' . . . . We must let the Greeks remind us that the fundamental purpose of our complicated and technical economy is the well-being of our families. This is why I'm so disturbed about what I see going on on Wall Street these days."

He proceeded to tear into the climate of greed that lies at the heart of the Wall Street scandals, saying:

"Corporations have become chips in a casino game, played for high stakes by people who produce nothing, invent nothing, grow nothing and service nothing. The market is now a game itself . . . . Corporations are now forced to watch the market more closely than they watch their customers. They are more sensitive to the street where you work rather than the streets where Americans live."

Gephardt linked the financial failings to political ones, saying:

"In government, our leaders say one thing and do another. They talk tough and then make bad deals for Americans behind closed doors.

"In your industry, the growth of an entirely new lexicon reflects the problems we have there: 'greenmail,' hostile takeovers, corporate raiders, poison pills and insider trading.

"It's a travesty that the best-known businessman in America is not the CEO of a major company or an innovative producer, it's Ivan Boesky.

"The government and the securities industry both must take steps to solve these problems. But we must also ask a more fundamental question. And that is a question of values. What do the recent scandals on Wall Street and the White House tell us about the values of the people involved? They tell us that these are people who are more interested in playing for high stakes than in working for the good of the nation."

Perhaps therein lies the major theme for next year's presidential election, the last of these self-centered 1980s.