Barry Goldwater is seldom identified with radical new ideas. But one of his comments during Sunday night's "60 Minutes" program contained the seed of an idea that, if adopted, would cause a substantial change in our form of government.

Harry Reasoner, who interviewed Goldwater, is a low-key journalist whose most prominent characteristics are his common sense, his restraint and his reasonableness. As soon as he began chatting with Goldwater, it was apparent that the senator was projecting the same image! In fact, Reasoner was soon asking, "Is this a new Barry Goldwater?" Had the senator mellowed with age?

Goldwater said no, but to this listener, and perhaps to many others he seemed refreshingly fair-minded and nonpartisan. He thinks President Carter has done well over-all, yet he pointedly declined to catalogue him with presidents like Nixon, who had been "lousy." On several specific issues -- the hostages, for one -- Goldwater said Carter had made the right moves.

This is a complete departure from traditional political attitudes and statements. Most politicians have nothing good to say about political opponents or about the polices they espouse, and nothing bad to say about political allies of their actions.

For example, when Pulitzer Prizewinning reporter Clark R. Mollenhoff began work on his latest book, "The President Who Failed," it was not his purpose to present a pro-and-con discussion, but rather an indictment of Carter's mistakes. A book of this kind has value, but only if its readers also familiarize themselves with books that put forward a contrary view.

To hear Barry Goldwater discuss Democrats who would make good presidents (Ed Muskie was his first choice) was a delightful change from the blind partisanship that usually marks discussions of this kind.

At one point, Reasoner was probing for Goldwater's throughts on why it's so difficult for Congress to enact effective legislation. I wasn't taking notes, so I can't use quotation marks, but the essence of Goldwater's reply was: Well, everybody is always so preoccupied with running for reelection. Every member of the House has to stand for reelection every two years, and a third of the Senate also has to run every two years, and the president has to run every four years, and, well, getting reelected is given top priority.

Long after the program was over, that comment kept rattling around in my mind.

What Goldwater found a hindrance to good legislation was precisely what the Founding Fathers had wanted. They insisted that members of the House return to the people for a renewal of their mandates every two years because they wanted the legislature to be responsive to the electorate. If you give a man too long a term as a representative, he may forget that he is not himself a power, he is merely a represntative of the ultimate power, the people.

However, the practical effect of frequent elections has been a pattern of almost automatic reelections in some districts, and therefore unbroken tenures that run on for decades.

The framers of the Constitution knew the value of retaining good public servants as well as the value of giving voters frequent opportunties to get rid of those who had fallen from favor. Their basic ideas were so good that one must think twice before suggesting that anything be changed.

On the other hand, the choices made at the Constitutional Convention were made more than 200 years ago. Changing times have already made severeal Amendments desirable, and there will surely be more.

One that is suggested by Goldwater's comments is an Amendment that would prohibit reelection to the Congress or to the presidency. One term and out! A member of either house would be eligible to run for any other office, including one term in the other house of Congress, but would not be permitted to stand for reelection to the same body. A president would also be permitted to run for any other office, but never again for the presidency.

How long should the various terms of office be? Many suggestions could be put forward. One plan might be one-fifth of the House to be elected each year for 5-year terms; one-tenth of the Senate to be elected each year for 10-year terms; and one term of six or eight years for the president.

The details could vary, but the basic remedy would remain unchanged. If Goldwater was on sound ground when he noted that a politician's preoccupation with reelection impedes the passage of statesmanlike legislative programs, the remedy must be to forbid reelection to the Congress.

Can you picture Congress agreeing to submit a Constitutional Amendment of this kind to the states?

If you can't, you have put your finger on one more argument for not permitting congressmen to perpetuate themselves in office.