Leaving aside the wisdom of his decisions or the soundness of his policies, the big knock against Jimmy Carter is that he lacked the one elusive, indispensable quality for the job. He didn't come across as "presidential."

Meaning what, exactly? It's hard to put a finger on, but you know it when you see it: a certain bearing, an air of authority, an easy self-confidence not to be confused with an air of infallibility; an instinct for order and organization; a capacity to inspire loyalty, command respect, resolve internal conflicts cleanly, impose discipline. Harry Truman, Dwight Eisenhower, John F. Kennedy -- each in his own way had that quality.

It comes down in the end to that over-labored word, leadership. And the test of it is the way a president deals with his immediate domain. In his management of the executive branch, Jimmy Carter was all too often perceived, from within as well as from outside, to be not acting "presidential."

It's a lot too early to be sure. But my hunch is that this may turn out to be the most important underlying difference (ideology, philosophy and particular policies and programs aside) between the Reagan and Carter presidencies.

Forget the Bonzo jokes, the Hollywood one-liners, the laid-back look. Something in Reagan's uncomplicated, unpretentious self-assurance suggests to me a fellow who has a feel for the importance of being "presidential" in ways his predecessor somehow did not -- above all in the area of those critical, all-encompassing issues having to do with foreign policy and national security.

Start with little things that matter.Like how, in private conversations with third parties, his aides referred to him. It may be old-fashioned, but it doesn't strike me as excessively imperial for subordinates to refer to the president of the United States as "the President," or The Boss, or whatever conveys a certain deference, if not affection. With Carter, outside of the Georgia inner circle (where it was, familiarly, "Jimmy"), it was usually, in a curiously detached way, simply "Carter."

Newcomers to the White House staff, career officials and even political appointees spoke of a curious absence of camariderie or a sense of common purpose. Midway in his term, one observed that "everybody around here is working for himself."

Much has also been made of Carter the compulsive, fine-tuning, nit-picking engineer, engrossed in details no president should be bothered with. In his finest hour at Camp David, he dazzled participants in the Middle East peace talks with his ability to hold his own with the technicians. But it was precisely this "unpresidential" preoccupation with detail, some would say, that led him to slight the larger problem of how to make the final accords acceptable to Arab leaders whose ultimate cooperation would be essential.

He was too much a moralist, others have complained, too much the True Believer, so persuaded of the rightness of his causes -- human rights, above all -- that he oversold them. And then, when the harsh realities set in and the comprominsing and qualifying began, he was forced into politically debilitating retreat.

Proceeding from generalizations to a crucial particular, consider the importance of articulating foreign policy with one voice. For whatever reasons, while demonstrating in the big 1979 Cabinet purge that he could sack people wholesale, Carter never could (or would) cope with this really big management problem in foreign policy. Only for a fleeting few months or so was he able to put an end to the power struggle between the National Security staff at the White House and the Department of State.

All along, the need for "presidential" management was self-evident. Now Reagan promises it. And the detailed way designated White House Counsel ("Enforcer") Ed Meese talks about it suggests he understands the problem well enough.

I am less impressed (or perhaps just confused) by the larger edifice of "Cabinet government" that transition-team member Caspar W. Weinberger says will be erected. As he described it in The Washington Post, it sounds formidable: the president as some sort of chief executive officer, delegating authority generously, forging consensus out of formal meetings with right-thinking if not entirely like-minded Cabinet chiefs, dictating to the great bureaucracies (with their clamorous constituencies) from the very top. It seems to fly in the face of human nature.

But never mind. The proof will be in how it works. For now it is enough to note that it has the welcome look, at least, of a design for something "presidential."