THE PRESIDENT'S daughter, Maureen Reagan, has characterized the president and his wife as being "just agonized" and "devastated" by the public family trouble being stirred by Mr. Reagan's son, Michael. Well, we can understand that: who would be anything but pained and embarrassed by the unremitting airing of this kind of personal business? But the Reagans should relax -- cease answering it and just let it happen if it must.

We know, as with all busybody advice profferred by outsiders to those in the midst of a family quarrel, that this is easier said than done. As the common retort from the oppressed and embattled family members goes, "Well, it's all very easy for you to say . . ." and so forth. But there are a couple of good reasons for the Reagans, whatever their feelings about the actual relationships involved, to take a cool view of the public outburst. One is that it is almost in the great presidential tradition. We say "almost" because the pulling and hauling with Michael Reagan does not quite rise to the horror of traditional presidential embarrassment by and conflict with and among family members. Think about Billy Carter or Donald Nixon. Think about the things Lyndon Johnson's brother said about him. Think through your recent and not-so-recent presidents and see if it isn't true that, compared with what has gone on before among first families and their in-laws, this one is really child's play, hardly worth a blip on the screen.

There is something else. In one respect, anyway, the great public out there and even the Beltway Brigade that lives right here are bipartisan and unanimous. It is in identifying with turmoils such as these, feeling a sort of "there but for the grace of God go I" connection with those in turmoil. In fact, people get rather competitive about these things: "You think that is something," they say with a sneer -- and then proceed to tell you of the horrendous crimes committed against them by a child or parent or sibling. It should be reassuring to the Reagans to know that the most common response you hear to their current family saga has been: "Big deal."