President Carter's decision to make an all-out push for energy legislation this year was based in part on a realization in the White House that Carter must soon achieve a major success or risk being perceived increasingly as a weak and ineffective President.

After the remarkably successful early months of the administration, filled with symbolism designed to build popular support for the new President and his programs. Carter has suffered a series of setbacks, the most serious of which was the down fall of his friend, former budget director Bert Lance.

The President has remained personally popular, but the public's perception of his performance in office has slipped badly with each new setback. The fruits of those early months of symbolism have dwindled and may, one administration official conceded, have been "frittered away" by a President and White House staff bent on accomplishing too much too soon.

In this atmosphere, Carter and his aides seized on energy as the issue to reverse the trend, not only because of its importance to the country but also because it is the only major administration initiative nearing a climax, for good or ill. If there is no energy program enacted this year, the President's first year in office is likely to be remembered more for its Symbolism and pace of activity than for any major accomplishments.

This view, and the importance it played in the all-out drive on energy were confirmed by sources both inside and outside the White House.

"The feeling here is that we've started so much, and finished so little," one presidential aide said. "That is why there is so much attention on energy. If we can finish the year with an energy plan close to what Jimmy Carter wants it will have been a successful year."

Another official said:

"There is a growing realization that if we don't succeed on energy it will affect our ability to succeed on all sorts of things later . . . There is no question we need a success, not only in terms of the polls but in terms of our eftectiveness on the Hill in the future.

"If they can walk over its on energy, what's to prevent them from doing it on other issues. The significance of this fight goes way beyond energy."

Carter's problems are not only on Capitol Hill, but also with the public he so assiduously courted his first months in office. The Harris Survey has shown a steady decline in the public's rating of the President's performance. In the latest poll, released early last week, more than half the people rated Carter's job performance as poor to fair.

Among the nation's five last Presidents, only one - Gerald R. Ford - had a lower performance rating at a comparable time in office.

A Democratic Party official confirmed that the poll findings are being echoed among party activists throughout the country. "We hear things like that - people saying what's the matter with Jimmy, why can't he get anything passed."

Patrick Caddell, Carter's pollster, said he would not comment until he sees further evidence, particularly the next Gallup Poll. But implicity conceding the President's central political dilemma. Caddell said, "His personal popularity is still very high. What is down is specifics on job performance."

The decision to concentrate on energy, putting other major initiatives to the side at least temporarily, may have been a painful one for the President. A supremely self-confident man. Carter came to office promising a competent government. He proceeded to launch a dizzying array of initiatives, from the Middle East and new strategic arms limitation talks to Welfare overhaul and the energy package.

His closest aides, such as Hamilton Jordan argued for months that this not only was the Carter style but that it also had side benefits. By attacking on all tronts at once, Jordan has said, the President managed to "slip through legislation creating a Department of Energy which otherwise might have been bogged down in controversy for months.

Perhaps so, but after 10 months in office, with the energy package in shambles and action on other major proposals not likely until next year, creation of the Energy Department and the fact that Carter has authority to reorganize the government seem to be fading in their importance.

What this combination of multiproposals and mini-successes has created one White House aide acknowledged is "a general atmosphere of total lack of confidence. There is a feeling we don't know what we're doing, that we're just flailing around."

Thus came the energy decision based, another aide said on the realization that "we can't keep all the balls in the air. One issue had to take priority and that had totake priority and that had to be energy."