WHAT IS IT that people who are not Ronald Reagan's natural born constituents are asking of the president these days? That he become a liberal? That he retroactively endorse all the thinking of the government that his own displaced last year? To some extent this does seem to be the wish of certain common scolds among us who have taken out after the president. Ronald Reagan, they complain, is not Teddy Kennedy or even Jimmy Carter. The interesting and consequential fact from Mr. Reagan's point of view, however, is that many of his genuine, longtime supporters think that he has turned into both.

If you read the conservative journals and pay attention to the current conservative dialogue, you will get the idea. There is a feeling of betrayal in the air. People who had a settled view on certain issues, say Eastern Europe or disarmament or Taiwan, and who were secure in the belief that these were the same as Mr. Reagan's views are raising hell about his policies. The absence of Messrs. Allen and Nofziger from the White House is not likely to reassure them. It is true, as the mollifying response goes, that Mr. Allen's replacement, William Clark, is also a man of the right; but he is not, like Richard Allen, a man associated over the years with the development of certain conservative foreign policy ideas in precisely the realms the new critics are worried about. And now there is this: talk of an actual increase in taxes or of a $100 billion-plus deficit emanating from their man--or, both.

So Mr. Reagan is at that familiar point in office when a president is compelled to face the truth that many of his pre-election ideas and pledges, no matter how earnestly arrived at, don't add up to the policy prescription he had hoped for. Some of his techniques don't work. Some of his ideas are impractical. Others are wrong. And still others take more time than he had supposed. All this sets off the opposition critics and the disappointed faithful, and the press loves it, and the sense of presidential isolation and besiegement grows. It is in dealing with this particular condition, which is endemic to the second year, that a president makes one of his most fateful series of choices, either demonstrating his real authority or kicking it away.

What are the ways to fail? One is to try to meet and disprove all the criticisms from every side, as Jimmy Carter sometimes seemed to do, to claim to be, impossibly, on the side of everything. The sorry IRS tax-break episode may have cumulatively created this impression of Mr. Reagan, eventually leaving everybody mad; but the technique is not typical of the administration. More typical, at least at the edges of the White House and among some of the displeased Reagan faithful, is the scapegoat- search approach. Thus increasingly one hears about how the bureaucrats and Foreign Service officers and other assorted "saboteurs" from the permanent government and the Bush campaign are subverting the administration, distorting the choices the president believes he has, keeping the truth from him and so forth. The people who push this line never seem to realize how damaging its implications are to the president they are trying to protect. We noted with interest that Mr. Reagan, presumably knowing this, was very firm yesterday in asserting that no one had kept him in the dark on the IRS regulation.

The IRS regulation affair brings to mind a final no-win technique for dealing with the disillusion and impatience and bellicosity that sometimes seem to engulf a president as he goes into his second year. It is to try to "buy" peace with one's disaffected constituents by tossing them victories on the so- called lesser issues--in this case, court and social equity issues that don't seem to cost much in the large daily march of political and economic events. Generally, this method tends to appease the most destructive and ungenerous instincts of a constituency for the sake of buying a little calm concerning their more cosmic disappointments. Was that what the IRS affair was about? We don't know. We raise it as a grisly possibility along with the possibility, rather remote it seems to us, that Mr. Reagan might also repair to the savage-the-critics approach.

All these tempting but unworthy responses, we note, have been tried out in recent years by a variety of administrations whose fortunes were made worse, not better because of them. Most don't seem responses characteristic of the Reagan temperament. But the president's alternatives are certainly neither restful nor easy. They require a president willing to stand firm (as he did with the air-controllers) or move (as he did with his remarkable initiative on theater nuclear forces) on the basis of real firsthand engagement in the issues. Then he needs to be prepared to stand up and take the heat.

Mr. Reagan does not have a good economic hand, to put it mildly. Nor does he have especially helpful allies or enemies abroad. Congressional leaders in his own party are getting fractious. Others in the states and cities believe he has made some big mistakes. And he has. Does he have the strength of character and purpose to rectify these mistakes? Can he turn his "communicator's" talent to establishing his authority in bad times? Can he really lead his followers, as distinct from making excuses to them or appeasing them at someone else's expense? The president will have to lose more popularity finally to gain his authority. This is the year in which we will find out more than whether Mr. Reagan is nice. We will find out if he knows how to be president.