It's that time again. In deference to sensibilities of long-suffering readers, I repeat the message printed in this space exactly a year ago.

Warning: Stop here if you can't stand to read another word about Ronald Reagan after his first now second year in office.

"Politics is just like show business," Reagan is said to have remarked when he became governor of California. "You have a hell of an opening, coast for a while, and then have a hell of a close."

Well, you certainly have to give Reagan credit. He has faithfully followed his own script. He had his dramatic opening. Not since Lyndon B. Johnson's early months in the White House did another president prove so successful in accomplishing his initial political/legislative goals. Even some of his ardent admirers will agree that Reagan coasted for a while afterward. Now, if you accept what you see and hear, he seems to be heading for a hell of a close, though not exactly what he had in mind.

It is becoming an all-too-familiar presidential phenomenon. Halfway through his first term, and what looks more and more likely to be his only one, another president finds himself besieged from all sides and in deep political trouble.

But even in this era of one-term chief executives, diminished presidential authority, increasingly volatile swings in mood by public and press about national leaders, and growing difficulties of governing, there's something alarming about what appears to be the unraveling of this latest presidency.

It can't have escaped your notice that the Chorus of Woe sings loudly about the failures of the Reagan presidency, real or imagined, these days. Wherever he turns, Reagan finds a new round of harsh criticism:

The New York Times, in one of its toughest commentaries since the Nixon Watergate period, begins a lead editorial bluntly: "The stench of failure hangs over Ronald Reagan's White House."

The Wall Street Journal, as staunchly supportive of the president as any major publication and an intellectual godfather of the supply-side economics he embraced, bleakly warns him that "the situation is steadily deteriorating, and can now be salvaged only by dramatic action."

The right wing rails against the cunning conspiracy aimed at capturing Reagan's soul by the dangerous moderates and, heaven forbid, political pragmatists. The Republicans in Congress grow openly more restive about the quality of his leadership and concerned about their party's future.

The press, until recently so gentle in its treatment of this president, produces a rash of stories delineating internal White House policy disarray and personal backbiting.

The White House, as if to confirm these reports, overreacts by placing a lid on contacts with the press, a foolish move certain to make things worse. The president's chief of staff publicly says he wishes that a Cabinet officer would resign, then apologizes for the statement. No sooner has that flap subsided than a Cabinet officer other than the one named, in an apparent surprise move, does just that, thereby reinforcing the idea that things are falling apart. Just as that dust settles, the president fires his arms control and disarmament director.

Then, further calling attention to a problem, the president said it's the press, not his administration, that's in disarray.

And over everything hangs the gnawing uncertainty about the economy.

From such a catalogue of trouble one would think the Reagan presidency suddenly has been overtaken by new problems. That isn't so. Despite the sense of discovery, there should be no surprises about the situation now facing this administration and the country.

Take one area of concern, the turnover of top personnel.

The latest departures only add to what already has been an extraordinarily high record of administration turnover. No presidency in memory has lost so many of its high echelon after a comparable time in office. Gone for various reasons in just two years are the original secretaries of state, health and human services and transportation and the president's chief aides for domestic affairs, for national security, for congressional liasion, for press and for political affairs. More key aides are expected to leave as Reagan's third presidential year begins.

Nor should the huge federal budget deficits being talked about in such fearsome terms take anyone by surprise. Critics consistently warned that the Reagan program of huge tax cuts, locked in over a four-year period all the while raising defense spending immensely, would produce precisely what it now has. So we finally see that George Bush ("voodoo economics"), John B. Anderson ("do it with mirrors"), David A. Stockman ("Trojan horse" and "trickle down") and Clark Clifford ("amiable dunce"), among others, were correct.

It is also now painfully clear that the administration forecasts were tragically wrong. The economy did not come "roaring back" as Treasury Secretary Donald T. Regan predicted it would a year ago. Nor have we even come close to realizing a balanced budget as the president himself said we would. By now, he said in his first budget message to the Congress, we should have been on the way to achieving a virtual budget balance with a surplus to come the following year. Instead, we've moved exactly opposite.

His first full year saw nearly a doubling of the previous single year's deficit high to well over $100 billion. We now face deficits of $200 billion this year and as much as $300 billion beyond that. This makes realistic the prospect that in only four years the Reagan presidency will have laid as much as three-quarters of a trillion dollars worth of new debt onto the country. Only in 1981 did the United States hit the trillion-dollar total debt mark--and that was accumulated after 200 years of national experience.

For Ronald Reagan, two elements are new about his situation today as opposed to a year ago.

Now, among virtually all segments of society, general agreement exists that present serious conditions require stronger presidential action. Now, Reagan himself, really for the first time in his presidency, is being blamed personally in the overall public discourse for his inability to deal effectively and aggressively with growing problems.

That doesn't mean his presidency is consigned to failure. His last act has yet to be written. It's not impossible to think he still can have that boffo "hell of a close" to his political career. But he has increasingly less time in which to signal change. Simply telling the press that he's in charge, all is well and all of the criticisms are spurious won't suffice.

The question for him, as power flows ever away from his office and back to Capitol Hill, is whether he can regain his lost command of events. If he cannot, by the time another year passes he could become an irrelevancy in the political process. The question for the country, as the complex problems multiply, is whether the drift and uncertainty that now settle over the Reagan presidency are tolerable.