From the president's point of view the news is good: One of those periodic upswings is on the way. You can feel it and read about it everywhere. Camp David, the smart money says, is bound to cast Carter in a larger, more awesome and better appreciated role, no matter how the negotiations turn out. Likewise, win or lose, he is widely expected to generate new sympathy in his pending end-of-the-session struggle with Congress. And above all, there is the turn in journalistic opinion, a predictable, even biorhythmic, event whose beginnings were perceptible well before Camp David or the White House-congressional showdown got in the news. Some reporters and analysts have stopped beating on Carter and started beating on each other for having beaten too hard on Carter in the first place. Pretty soon it will become an anvil chorus. And then it will change back - of that you can be sure.

All right, I am being cynical. But the point seems to me beyond dispute. We - the press, the politicians, the public - indulge in these wild, day-to-night swings of mood about a president. He is the worst; he is a failure; he has, in the Supreme Court's memorable phrase, no redeeming social value - none . And then come the misgivings, the hey-wait-a-minutes: He's our president, love him or leave him. And besides, if you're so smart, what would you do about -- (oil, inflation, Scharansky, Castro, George Meany)? And anyway - this is meant to be the knockout punch - all this criticism is just coming from elitists and similar well-paid rabble; the people . . . ah yes, the people . . . know better. They respect and admire the president. This particular bit of persiflage, I have noticed, is regularly invoked when the president's standing in the public-opinion polls is registering somewhere between zero and minus 4.

But for better and for worse, whether we are hugging a president to death or pronouncing him hopeless, we tend to be reacting mainly to each other, not to the president. And the president, any president, becomes in this connection little more than the national doll baby: that unfortunate shell-pink creature, missing half its ghastly hair and at least one limb, on whom little girls, in a capricious outpouring of punishments and slurpy affections, project all manner of behavior, vice and virtue that has nothing to do with anything. Or at least nothing to do with their pitiful, much-kissed and thoroughly battered plastic victim.

Why this should be, I not know. But there is a kind of overwhelming force to it whose origin seems to lie outside any actual conduct or record of the president in question, whoever he may be. Possibly it's just matter of trends, boredom and the quest for change. Johnson and Nixon and Ford all seemed to me to experience highs and lows, fevers and remissions that were based on the flimsiest of stated explanations. I mean that during and within the unfolding of the large political actions that defined the presidency of each, there would come these random swings of feeling, reinforced by and reflected in a great gush of media commentary announcing that the president was staging a fantastic comeback or (alternatively) going down the tube.

Well, it makes life more interesting and dramatic; there is no question about that. And it gives us all a chance either to put down some crowd of critics we don't like or to establish ourselves as cutting-edge, maverick, original types: "Listen, you're going to think I'm crazy, but I say Carter's doing a fine job and let's leave him alone."

Beyond that, my guess is that the process has a great deal to do with a universal need to personify the government and the state, to make a single flesh-and-blood person the dramatic embodiment of our national well-being or malaise. Adoring or despising Jimmy Carter may require oversimplifying all those ambiguous and often mutually contradictory aims we have for the society. But it sure beats trying to make sense of the two-steps-forward, one-step-back issues in which he and the rest of the government are involved. And in any case, despite our endless protestations to the contrary, I think some part of all of us wants a larger-than-life president - huge in his faults and majestic in his virtues or, on alternate days of the week, both.

In other words, we want a pattern and we want a king-size leader and we have settled on rather tinselly, superficial way of attaining the two. To me, the irony, as well as the interesting, if disturbing, question is this: How is it possible that an institution and an individual so heavily, even oppressively, covered by the media continue to elude reasonable, straightforward analysis? Why is it that, instead, the presidency and the president tend invariably to become little more than stage props for these recurrent ritualistic swings of "opinion"? The White House press corps grows in size. The press raft, no less, bobbles down the Salmon River in the wake of River Raft One. The talk shows, the parlors and pool halls are the setting for appraisal, argument and concern related to the incumbent president. And yet the judgments, finally, have a uniformity, a cyclical nature and a life of their own, seemingly independent of the life of the president.

Not that officeholders don't try to mix into the fun and take advantage of it. Carter is no different from his predecessors in attempting to manipulate the current upbeat signs, posing and posturing a little here, faking a little there, all in the name of seeming to be your courageous, maligned but masterful president. In some ways, to be sure, he is those things - and in other ways he is anything but, a compexity that none of us much likes fooling around with or having to fit into our appraisal.

Presidents, of course, are not inclined to see it that way, and even less are their staff and associates. Woman and girl, I have never known a White House that didn't perceive the down-swing as an unfair, mindless exercise in press groupthink and public confusion, and the (equally automatic) upswing as the restoration of justice, fair play and good sense at last. And I have also never known a White House that, euphoric with the new positive mood, did not somehow, in a frenzy of over-confidence, do something rash and foolish in response - on the theory that, once and for all, happy days were here again. An overreaching, a big mistake, a settling of scores . . . something that became the trigger for the next turn-around.

As Jimmy Carter moves presidentially through the sylvan setting of Camp David and poses for battle-dress photographs in the conduct of the fall offensive against a misguided House and Senate, he could do worse than to reflect on the fickleness of the spectators who have produced this sudden good fortune for him - and on the unhappy truth that this too shall pass.