I have been contemplating the anxieties being everywhere expressed about the American government this autumn, and they all lead me to the same conclusion. What this country needs in the presidency just now is a man who is a really good actor. Do we have one? It's not clear.

There is, of course, a sense in which this is always true and another in which it never is, and both require a word of explanation. All presidents need certain stagy skills if they are to be taken seriously. They need presence, size, a flair for drama and a gift for communication (which is much giggled at in Reagan by people who are always lamenting its absence as a default of leadership in others). To a very great extent, the modern presidency is a job of conveying signals, moods and impressions, and making things happen by the way you do so. It's where the power is.

That is the positive side. The negative--the respect in which no president should be an actor--has to do with the common misperception of both acting and politics as debased or duplicitous talents, as ways of dissembling and falsifying what is real, as pretense, fakery and manipulation. In this country, we have made a minor industry of this conception of politics as imposture. There are the finger-to-the-winds daily surveys, the endless changes of "position," the clever and seemingly real "personalized" form letters, the image- crafting, the ultimate creation of your candidate as an impersonation of the candidate he thinks you want him to be. That is neither authentic good acting nor authentic good politics, but it often passes for both.

Franklin Roosevelt and Ike had the proper acting gift. Richard Nixon lacked it. Ditto Carter. And the latter two, although very different in big ways, were alike in that when they tried to exercise an acting talent they didn't have, it was stilted and obvious and embarrassing, good for a huge, collective, nationwide squirm.

Who are the leaders who have most successfully integrated the actor's and the politician's arts, made them work together to their purpose? Fidel Castro and Anwar Sadat surely get into the finals, although I take as the paragon, and my model, Lech Walesa. Walesa is a natural performer. He knows how to move an audience and a situation, is in fact always working the crowd, sending messages, acting on a stage of which he is aware. He may have risked too much --we still don't know--but he is a great instinctive actor-politician. Think of him and then think of that hair-sprayed, poll-ridden character who is running for Congress in your area and you'll get the idea.

And now along comes Ronald Reagan, our first professional actor, to the presidency. He comes at a time when the signal-sending imperatives have never been more complicated and urgent. Wall Street demands to be reassured. Its reassurance evidently can only come at the expense of other elements of the society who, accordingly, need also to be reassured that they are not being deprived and misused for the monetary sake of the big boys.

Then there is the related matter of defense. Jimmy Carter, I suspect, would understand far better and in far greater detail than Reagan the precise arguments about the various weapons systems and their development that are the subject of much debate now. But Reagan will probably be better than Carter could have been at making the best of the situation in terms of messages sent. He needs to convey resolution at home concerning budget deficits and any number of other hot issues.

It will have occurred to you that the problem here is that the messages he feels he needs to convey to these different constituencies are in some key aspects directly contradictory. Cut the defense budget to reassure Wall Street. Raise it to tell the ill-wishers abroad you mean business. Reagan, like all of his recent predecessors, is at once the propounder and victim of a kind of Tinkerbell economics, concerning which the key question is Do you believe? He needs to convince the suspicious and the self-protective that a theory will work--in order to make it work. How much can he revise it without conveying the message that he himself doesn't hold with it anymore?

Actually, I don't think it is the theology of defense spending or supply-side economics that Reagan needs to argue or explain to his various more and less friendly constituencies. That is because I don't think any of those damfool theories about how if you only do this that will happen bear anything but the most crude and general approximation to the truth. What Reagan needs to convey is, first, that he knows what he is doing represents at least in some general way the shared conception of what is just, what is right. These cannot be simulated, campaign-consultant-school impressions. They need to be authentic with the man to be successfully projected from the stage. And both are what is in question just now. This, I think, is true, even when you have corrected for all the self-serving and/or self-indulgent criticism that is being heard.

Here is what a president-actor must be able to do: he must be able to communicate the confidence of the great immortal message from the cover of the old Mad magazine ("What, me worry?") without looking like Alfred E. Neuman. On the social-equity questions, the "smart" boys are once again arguing that the real political heartbeat of this country is an ungenerous one, that there is political currency in kicking around the welfare set. My observation is that for all the tough talk you hear on these subjects, a political leader had better look out for violating a much deeper rough sense of social justice people have about misusing those who can't fight back.

So Reagan, by this reading, needs to persuade people that his overall economic strategy is well-intended, not a scam, and that he is not bugging out on it--not clutching, not reversing position at the first sign of trouble. I'm not one of those whose voice sings back to the Peter Pan inquiry: can't say I'm a believer in the theory Reagan is basing his hopes on. But in some sense anyway, the play's the thing. He can only succeed--and may--if he can project, persuade, get the audience to believe him.