IT IS A wondrous aspect of the American presidency that the holder of the office seems to be held accountable for nothing--or everything. Neither view is especially plausible, but that has never stopped countless Americans from ardently arguing one or the other or, sequentially, both. The idea that a president is responsible for all things (usually all things terrible) large and small does not take root until fairly late in an administration when the honeymoon has not just passed but has actually given way to midnight crisis. It is at this point that presidents, mystically, as if they were some all- powerful, mischievous pagan gods, get credit for everything from falling moral standards to falling snow, not just a falling GNP.

The opposite view, however, is no less mystical, no less trusting, no less naive and self-deluding. It is the insistence that the Great Benign Leader cannot possibly know, let alone be accountable for, the outrages that are being visited upon the righteous and the faithful. If only he knew. That is, pitifully, more or less where some of Mr. Reagan's depressed constituents are now. Yesterday a couple of them, Howard Phillips and Richard Viguerie, appeared on David Brinkley's television program espousing this general perception. Ronald Reagan thinks right, is a fine and decent and benign right-winger, in their terms. Yet somehow his presidency is doing all these rotten (from the Phillips-Viguerie point of view) things.

It is touching, this faith, but also foolish. The big questions that are troubling people like Messrs. Phillips and Viguerie along wtih other elements of the original Reagan constituency are fairly well- known. They concern, for instance, whether the administration should not have taken much stronger action against the perpetrators of the Polish repression--calling in debts, cancelling scheduled U.S.- Soviet talks. It also concerns whether it is possible, without an increase in taxes or a cutback in popular middle-class entitlement programs such as Social Security, to avoid elephantine hundred-billion-plus deficits. The president, it is argued, is not being true to his old, clearheaded, unambiguous self on these questions, but rather is being led into a morass of temporizing and faulty decisions by people who have pulled the wool over his eyes or otherwise prevented him from understanding what is going on.

But if Ronald Reagan does not know the arguments for and against, say, stronger intervention in Poland or for and against the particular economic solutions favored by his original constituency on the right, he must be the only American over the age of 12 so unaware. And of course this is not the case. It is one thing to say, as many of the president's critics on all sides do, that he is far too casual about detail and fact when he speaks. It is quite another to suppose that he doesn't know what is being done on the big issues in his name--and by whom and with what authority and why. Mr. Reagan's critics' complaint is . . . with Mr. Reagan. Until they cotton on to that fact, they will be touching and even in some respects entertaining, but not especially instructive as a guide to what is going on.