Between 1960 and 1980 the percentage of Americans living in poverty was cut by more than half. In the last year of Dwight Eisenhower's second term, nearly one out of five Americans was living in poverty. By the last year of Jimmy Carter's only term, that figure had dropped to one American in 15.

That change, in only 20 years, constitutes a historic achievement in which Americans can take considerable and justifiable pride. Essentially only two political groups of Americans remain unwilling to recognize that record of improvement and to take either pride or pleasure in it: conservatives and liberals.

That has not always been the case for the conservatives, who began this decade by quoting Ronald Reagan's domestic policy adviser, Martin Anderson. He wrote a book conceding that the liberals' Great Society programs basically succeeded. More recently, the conservatives have switched to quoting Charles Murray. He later wrote a book charging that the liberals' Great Society programs failed. Conservatives are flexible about everything, except their conclusion, which is that domestic federal programs can be cut without concern because a) they have obviously succeeded or b) they have obviously failed.

But what is the explanation, beyond that of terminal joylessness, that prevented the Democratic liberals from claiming credit for that record of national progress achieved under Democratic programs and supported by Democratic congresses, of which the nation had noth0? The Democrats' problem has its origin in the very legislative rituals and rhetoric under which those antipoverty programs originally were authorized and funded.

Here's how the legislative process worked during those remarkable "can do" days of the 1960s: You and I, who were totally committed to the elimination of illiteracy among Americans, advocated a modest federal program that we were confident could achieve that happy objective. Recall that era when confidence in our collective ability to accomplish noble ends though public efforts prevailed, so the chances were pretty good that we could find a friendly congressional subcommittee before which to make our case. The making of that case required our being able to present a dramatic "set of horribles" -- graphic, personal tragedies -- that could have been prevented by the funding of our federal program. If our "set of horribles" was compelling enough, we got our funding. We went to work. We helped older people learn how to read. And then something happened.

Programs, at some point in the political process, became values. Legislators proved their commitment, their compassion, their caring by voting for $50 million more for Head Start or pollution enforcement than the administration had requested or than Congress had appropriated the previous session. Decency was measured by an incremental increase in appropriations. When Jimmy Carter made the altogether reasonable proposal to review all programs through zero-base budgeting, he was attacked -- by Democratic liberals -- as heartless and uncaring.

To justify the increased appropriations (which you and I welcomed), we could not come in with boasts of our mission's having been accomplished. No, what we had to uncover was more woe to vindicate an enlarged effort at a higher level of funding. Thus, those programs came in with more bad news of previously igeprivation. That was how the system operated on Capitol Hill, and soon that same language of crisis found its way into Democratic Party debates and platforms.

Contradicting the weight of evidence and the personal observations of many citizens, liberal Democrats preferred to deny that Americans had become, as a result of programs they had advocated, healthier, better fed, better housed, better educated and residents of a cleaner and more wholesome physical environment. Instead, the Democrats' message remained a litany of problems. After a while, people got tired of listening to the Democrats. And who celebrated an improved America to his immense political advantage? That's right, the same fellow who had opposed all those costly intrusive federal programs, such as Medicare and the civil rights acts: Ronald Reagan.

A lot of liberals are now just learning that even the most compassionately generous of citizens eventually grow tired of hearing how their tax dollars have failed to solve any problems and how things have grown worse instead of better. When the unfinished public business is put in terms of reminding us what we have already achieved together -- the great schools and communities we have built and the crushing human burdens we have collectively lightened -- then the remaining task becomes more doable.