Reagan's midterm testing -- more rigorous than most

President Reagan is fighting to preserve the momentum of his administration and to confront difficulties on the international, economic, and political fronts. Top administration leaders are confident they can surmount problems. But rarely has a US government been tested so seriously and on such complex subjects at midterm.

* With a reconstituted negotiation team, the administration launches new initiatives at Geneva, while an anxious Europe watches the Washington-Moscow maneuvering. Vice-President George Bush swings through Europe to explain America's position.

* At home, Mr. Reagan formulates a new tax program. It is a critical moment - there is 10.8 percent unemployment, a prospective $200 billion budget deficit, a dubious Congress waiting to hear State of the Union and budget messages, while abroad there are shaky foreign loans, the threat of a credit crunch, and global recession.

* On the US political front Mr. Reagan has made changes in his Cabinet and made gestures toward reducing the military budget. Observers note that Senate Republican leader Howard H. Baker Jr. of Tennessee may be positioning himself for a possible 1984 presidential bid. Meanwhile, half a dozen Democratic presidential hopefuls have virtually begun the 1984 race at California's state Democratic convention in Sacramento (see Page 6).

In the tension over the 1984 budget, Washington heard unattributed complaints of floundering and lack of direction. Changes in Cabinet structure and other developments indicated that Mr. Reagan was aware of current problems and was realigning his position. On the economic side Reagan was getting advice from all sides, much of it conflicting. After a 1980-81 flirtation with so-called supply-side economics and the hope of combining a balanced budget with tax cuts, the administration has now come to a more conventional view. Some administration members are contemplating higher taxes as a means of dealing with deficits.

President Reagan intervened directly to counter reports that his administration is losing control of arms negotiations abroad and the economy at home. He assured allies he will consider ''every serious proposal'' from the Soviets.

He dramatically appeared at a surprise press conference Jan. 14 and made a spirited defense of his administration. His bold frontal manuever answers some critics whose reports have been a feature of the recent Washington scene. It came on the heels of shifts in the Cabinet and dismissal of Eugene V. Rostow after a stormy tenure as director of the Arms Control and Disarmament Agency.

The President threw journalistic criticism of ''wavering'' in his administration back at the press, charging that the ''disarray'' lay not in the White House but in recent news reports. He said he encourages a variety of viewpoints from aides, ''but then I make the decision.'' Various options being presented on the budget, he said, are being reported as rumors that decisions have been made, when they haven't.

But even the conservative Wall Street Journal, which would normally support a Republican president, has been critical. Reagan should change political ''reality,'' it says editorially, not accept it. On Jan. 12 it told him:

''You are in political and personal trouble because in the past year you have increasingly accepted political reality; to recover you need to go back to challenging it, as you have most of your life. The Congress may accept 'political reality,' but your job is to change it. Mr. President, that's why we hire presidents.''

Herbert Stein of the University of Virginia, a former economic adviser to Presidents Nixon and Ford, told the National Press Club here:

''The danger is not that the administration will stick rigidly to the policies with which it came into office. It could not possibly do that. But it is oozing away from these initial policies, reluctantly and haltingly and without any evident sense of new direction. At the same time the opposition does not offer any discussable alternatives but mainly reiterates old positions in which even it no longer has much confidence. So economic policy is adrift.''

A period of testing often comes at midterm in an administration, and today's turmoil is complicated by uncertainty over whether President Reagan will seek a second term. Preliminary public opinion polls show that affable Mr. Reagan remains popular with the public. But they also show that he has fallen behind Democratic front-runners.

Only limited confidence can be put in such estimates, however, old-timers caution. They recall how President Truman won in 1948 after being counted out by every poll in the country.