It seems almost an age away now, but it was only last December when a lead editorial in the New York Times detected a ''stench of failure'' rising from the Reagan White House.
And in that same month of December a Gallup poll showed Sen. John Glenn of Ohio beating President Reagan by 54 to 39 and former Vice-President Walter Mondale doing the same by 52 to 40.
But that was also a time when unemployment was still getting worse and the fresh shoots of a widely heralded economic recovery had not yet been detected.
What a difference three months can make in the kaleidoscope of popular thinking and political prospects.
There are still brisk arguments over whether the ''recovery'' is temporary or long-lasting. Pessimists are those who think that it will eventually be smothered by the weight of the huge deficits which present administration policies seem to point to for the last half of the decade. Optimists are those who think that the decline in oil prices will be sufficient to head off the weight of the deficits and hence prevent a return of double-digit inflation in the United States.
The essential fact is that the economy has ceased to be the central presumed issue in the calculations of politicians. There can be no doubt that American industry is feeling the sturdy beginnings of a revival. American management has been goaded by the recession into doing a lot of long overdue things. Antique plants have been scrapped. New plants using new technologies have come ''on line.'' Surplus labor not only on the factory floor but also in the ranks of management has been discarded.
American industry is today leaner, livelier, and more efficient than it was before this latest recession jolted it into serious rethinking of priorities and habits.
This has not removed unemployment as a problem. It is there calling for more action than has yet been taken. The numbers of those unemployed is roughly the same as those forced into unemployment by the mechanization of agriculture during the '20s and '30s. It took a long time for the American economy to absorb those millions (probably about 10 million in all) who were turned off the farms and found their way mostly to the slums of the big cities.
There will probably be a serious problem of retraining those who have been pushed into unemployment by the modernization of American enterprise in these times. Such large numbers cannot be retrained or relocated quickly even with the best efforts of government. But unemployment has ceased to be the central political issue for the factual reason that industry is regaining its health and is beginning to rehire.
As of right now, unemployment and the state of the economy have ceased to be politically damaging to the administration. The proof is in the fact that the herd of hopeful Democrats has stopped using those issues against the administra-tion. They are forced by events to turn to the environmental issue (should more than Mrs. Burford be jettisoned?), does President Reagan prefer guns to arms control, and are there damaging conflict of interests conditions in and around the Reagan White House?
This week Mr. Reagan reaffirmed his confidence in Thomas C. Reed, a deputy assistant in the National Security Council to William P. Clark. Mr. Reed is under investigation by a federal grand jury in New York and also by a House committee on oversight.
Presidential reaffirmation of ''full confidence'' is beginning to be less than welcome. Mrs. Burford had it a week before she was pushed into resigning. Mr. Reed was accused in 1981 by the Securities and Exchange Commission of using inside information to turn a $3,125 investment in stock options into a gain of $ 427,000. He was required to return the gain and sign a pledge never to use inside government information for personal profit again.
Probably the environmental issue will continue to be useful to Democrats and painful to the administration for some time. And there is little doubt that at the moment the Democrats have an advantage on the peace and arms issues. Polls show a big majority wanting arms control and thinking that the Reagan arms budget is too large.
But Republicans can take comfort from the fact that the President could defuse both those issues if he should within the next 12 months conclude an arms control agreement with the Soviets which would in turn permit him to cut back on the arms budget. He has within his hands the ability to do just that.
The above, plus the windfall of the continued decline in oil prices, makes for a big improvement in Mr. Reagan's political situation. The Democrats are a long way from a clear win in 1984.