One of the most memorable experiences of my life is the two weeks I spent in Independence, Mo., in 1970 talking to Harry Truman, which is why I reacted with special dismay to the recent story about the former president, William Clinton, making tens of millions of dollars as a speaker and business consultant since he left office.

I had come to Independence with the president’s daughter, Margaret Truman Daniel, to help her research a biography of Truman in his presidential library. In the evening, after dinner, we discussed his presidency. Gradually, our talks broadened to the office itself. I soon realized Truman had given deep thought to the topic.

Truman believed the American presidency was the most significant political office ever devised by human beings in 3,000 years of politics. He had devoted not a little of his library’s exhibits to an extended lecture on the office, its many sides, its diverse powers, and its awesome responsibilities. He could point to its roots in George Washington insistence that the office was central to a successful federal government.

Truman saw a strong presidency as vital to America’s political health. Without it we had congressional government, which Truman considered more dangerous to the future of America than the machinations of the Soviet Russia and Communist China combined. The reason was simple but profound. In Congressional government, no one is responsible. The politicians act as a group and are subject to pressures and emotional appeals to which they frequently succumb.

Anyone who damaged the presidency earned Truman’s contempt and when he was in a strenuous mood, his denunciation. He was particularly hard on presidents who committed such an offense. He could savagely annotate their failures, from James Buchanan to Ulysses Grant to Warren Harding. In 1970, he was merciless toward Lyndon Johnson. “No guts!” was the way Truman summed up the big Texan’s chief executive years. Johnson had let protestors drive him from the White House — a deplorable act of presidential cowardice, according to Truman.

Truman thought Johnson should have run for reelection in 1968, as Abraham Lincoln had run in 1864, when his presidency was under savage attack in a far more terrible war. Truman had no doubt that Johnson would have won — and North Vietnam, intimidated by this evidence of the determination of the American people, would have come to the bargaining table. America would have concluded a peace that made South Vietnam an independent county, like South Korea.

Truman had no illusions that presidents sometimes have to pay a price to do the right, the courageous thing. His poll numbers were almost subterranean when he left office in 1952, because of his insistence in achieving a free South Korea. He came home to Independence, that marvelously symbolic city, with very little money and no income worth mentioning beyond an advance for his memoirs. There were no pensions for presidents in those days, and no secret service protection.

Soon Truman was bombarded with offers of figurehead jobs with cushy salaries as chairman-of-this and president-of-that. His answer, invariably, was no. “The presidency is not for sale,” he said. His respect for the office was so immense, so central to his mind and heart, that he could not and would not risk tarnishing it in any way. He would not even accept fees for a speech, beyond travel expenses.

Now we have Mr. Clinton, making $51.9 million for speeches in the seven years since he left the presidency, plus $12.5 million from his murky “consultant” relationship with Yucaipa, the Los Angeles investment firm run by his friend, the billionaire Ronald Burkle. Mr. Clinton also earned $3.3 million for advising the head of the database firm InfoUSA, Vinod Gupta, who has also given his friend Bill $900,000 worth of trips around the world in his private plane. Mr. Gupta’s stockholders have accused him of looting the company for Clinton-linked outlays.

For this ex-president, the mantra has never been, “The presidency is not for sale.” To all comers and buyers, Mr. Clinton’s motto has been — and still is — “How much?”

It is not hard to imagine what Truman would have to say about the damage Mr. Clinton has inflicted on the office of the presidency. It is more difficult to picture his incredulity if he were alive today and watched millions of voters and thousands of reporters and editors and TV commentators contemplate with equanimity the prospect of returning this man to the White House in the guise of voting for his wife.

Mr. Fleming most recent book is “The Perils of Peace, America’s Struggle to Survive After Yorktown.”