The whole mess began when Jimmy Carter, who entered the national consciousness by saying he’d never lie to the American people, said that the Bush administration’s foreign policy was “the worst in history,” adding that President Bush’s invasion of Iraq was “a radical departure from all previous administration policies” and suggesting that Mr. Bush was the lone American president who didn’t honor the separation of powers.

Then he said he didn’t quite mean it the way it came out. The polls suggest that some, perhaps a great many, people believe what Mr. Carter said the first time. My guess is that there isn’t a soul on the face of the Earth who believes what Carter said the second time.

Best former president

For one of the few times since he climbed down from the mountains to counsel Americans on their malaise (he didn’t actually use the word), the country was talking about what Mr. Carter had to say. He is perhaps the best former president we ever had, and won a Nobel Peace Prize for his work, but he was, by consensus, not the best sitting president.

The Bush White House was not pleased by Carter’s remarks, with Tony Fratto, the deputy White House spokesman, calling them “sad and reckless,” adding, “I think he is proving to be increasingly irrelevant with these kinds of comments.” Even some of those who thought Mr. Carter was speaking truth to power wondered whether he might have spoken not wisely but too well.

All this caused such a stir because these things are not done, at least in the popular imagination. Trashing a sitting president is something for a radio talk-show host to do, not a one-time commander in chief. This is supposed to be part of the shared burden and responsibility of the office.

That shared burden and shared responsibility are what drew Bill Clinton and George H.W. Bush together; this very month they were pictured laughing together at the commencement ceremonies at the University of New Hampshire, where they were awarded honorary degrees for the humanitarian work they do together. In the 1992 campaign, Mr. Clinton said some savage things about Mr. Bush’s stewardship of the economy. But out of office they are just two men who understand how tough it is to be president, what with the press carping every day and members of the Congress acting like immature jerks.

Both divisive and unifying

That same burden and responsibility drew Mr. Carter and his predecessor, Gerald R. Ford, together as well. The 1976 campaign between the two of them was bitter and brutal, so much so that aspects of it are still painful to recall. But years later they became friends, confidants, co-conspirators.

This friendship did not prevent Ford, in remarks published after his death, from having harsh words about Mr. Carter: “I feel very strongly that Jimmy Carter was a disaster. He was certainly the poorest president in my lifetime.”

All this is to demonstrate that the men who have shared the presidency also have shared choice words about each other. They are like other men. They believe their successors, predecessors, peers and rivals are fools, crooks and louts. Woodrow Wilson once described Chester A. Arthur as “a nonentity with side whiskers.” Who are we to think otherwise?

No one speaks ill of Harry Truman today, but Truman spoke ill of almost everybody. “Nixon is a shifty-eyed, goddamn liar, and the people know it,” he said, and he was right. “The general doesn’t know any more about politics than a pig knows about Sunday,” Truman said about Dwight Eisenhower, and he was wrong. “The trouble about the president is that he lies,” Truman said about Franklin Roosevelt. That was true, but that may not have been the trouble with Roosevelt. (How do we explain this to the kids?)

Indecision draws derision

Presidents don’t like indecision – not Mr. Bush’s problem, by the way – in other presidents. It comes with the presidential character, sometimes emerging before a president even has the job.

Two years before he would become president, Theodore Roosevelt said that William McKinley “has no more backbone than a chocolate eclair.” Of Benjamin Harrison, TR said: “He is a cold-blooded, narrow-minded, prejudiced, obstinate, timid old psalm-singing Indianapolis politician.” Ulysses S. Grant once said of James Garfield: “He is not possessed of the backbone of an angleworm.”

Presidents’ predictive powers are no better than others’. “Can you imagine Jerry Ford sitting in this chair?” Nixon said, not knowing that, before long, millions would do just that, and with an enormous sense of relief. “This man will never be president. The people don’t like him,” Eisenhower said of Nixon. Half right. Then again, it was Nixon who said that “Reagan is not one that wears well.” Not right at all.

No two ex-presidents engaged in a more poignant exchange of correspondence than John Adams and his successor, Thomas Jefferson. But Adams once said that “Mr. Jefferson tells large stories,” and Jefferson once described Adams as “vain, irritable, stubborn, endowed with excessive self-love.” Both right.

So, too, was Warren G. Harding, who was right about almost nothing. And yet he described one president as being “not fit for this office,” a man who “should never have been here.” He was talking about himself. A little modesty and self-knowledge never hurt anybody, including a president.