A week ago Friday, Jody Powell strode into the White House press office with a prepared statement from President Carter.

The President, his press secretary said, was seriously concerned that the oil and automobile lobbies on Capitol Hill were dismantling his energy program. Should the "special interests" prevail, he warned, the American people would pay the price.

Powell's statement marked that beginning of the most crucial week so far in Jimmy Carter's still evolving relationship with the Congress of the United States. It had begun badly, the day before the Powell statement, with a series of setbacks to the Carter energy plan in congressional committees. There were predictions that a mighty confrontation between the White House and the Congress was at hand.

A week later, the predominant view was significantly different. Carter came through the first series of key skirmishes with Congress with a mixed scorecard, but certainly better off than many expected at the beginning.

After the initial setbacks to the energy plan, the President's lobbyists rallied and turned back an even more ominous attempt by the oil companies to keep some of the revenues from wellhead tax on oil for themselves.

Carter struck a bargain with the congressional leadship over a spending bill for the Labor and Health, Education and Welfare departments, and it appeared to be sticking. He continued his crusade against what he called "unnecessary" water projects, losing a battle but by such a surprisingly close margin that he might yet win the war, or at least an acceptable peace settlement.

The process itself illuminated some of the mistakes the President has made in dealing with Congress and for which, White House aides now concede, the administration is paying a price. And the experience, it was clear from conversations with White House officials, is gradually coloring the views of presidential aides about some of Carter's cherished notions - like the nobility of "Cabinet government," with a minimum of White House interference, and the ease with which a Democratic President's personal popularity can be used as sledgehammer against a Democratic Congress.

But if, by the end of last week, morale was high among Democratic congressional leaders and key White House aides, no one was predicting the end of the unusual tension between a Democratic White House and Congress that has marked the first months of the Carter administration. A confrontation remains possible, even if there seems to be less enthusiasm for that inside the White House than may have been the case earlier. The President, probably sooner rather than later is going to veto a major bill and some of his aides think that might not be a bad idea.

Carter's relations with Congress are different. They are different from what some expected before he took office, for Carter has proven not be the singleminded, uncompormising chief executive he was said to be as governor of Georgia.

But when early compromises led some to question just how tough this new President really was, Carter last week proved, in beating back the oil industry ploy and coming close in his water projects battle, that he can and will fight.

His congressional relations are different mostly because Congress changed during the last eight Republican years - it is much more assertive and independent, a fact now well understood in the White House - and because Jimmy Carter is a different kind of Democratic President.

"We won some an lost some," Powell said of the last 10 days. "What's clear is that there is a process. There is going to be compromise. People had gotten to the point of thinking there wasn't going to be a process - that it was going to be the President and Congress standing at opposite ends of Pennsylvania Avenue chucking rocks at each other."

"By and large I feel good about it," Carter's chief political adviser, Hamilton Jordan, said at the end of the week of testing with Congress.

"Democratic Presidents are supposed to act in predictable ways, but that's not necessarily the way it is with Carter," he said. "He's supposed to be compasionate, but no so concerned with balancing the budget. To some people, those things are contradictions. But that's just the way Carter is."

The way Carter is, it is widely agreed in the White House and on Capitol Hill, has contributed to the underlying tension of his relations with Congress and probably to the anticipation of an inevitable clash.

Politically, the President arrived in Washington as the outsider, lacking experience in Congress and the net work of friendships and understandings that produces. He had not tied his campaign closely to others in the Democratic Party, and so arrived on the scene still a stranger to the congressional branch of his own party.

Personally, Carter is not of the congressional mold. He is not a backslapper or wheel dealer, the king of President Congress has grown accustomed to.

"Some politicians like Tip O'Neill relish the give and take of politics - the getting jobs for people and all that," one White House official said. "Carter just doesn't."

The net result of this - the political and personal gulf that still separates Carter and Congress - was summed up by an administration official who works Capitol Hill regularly.

"There just isn't a residue of good will up here for Carter," he said. "If you ask people to vote with him, they'll say, 'All right we'll go along, but why the hell should we.'"

Frank Moore, the White House congressional relations chief, says his boss is a "technical man," another way of saying he is not good ole boy from the Ways and Means Committee. That characteristic of the President was never more evident than in the early handling of the energy plan and may have contributed to some of the early defeats.

The administration energy plan was the creation largely of two technical men - Carter and his energy adviser, James R. Schlesinger Jr. But once drafted and introduced, it remained in the hands of technical men, and not the political and congressional operatibes whose job it is to shepherd legislation through Congress.

So when the time for the first key committee votes arrived, Capitol Hill was swarming with administration lobbyists, but they were, by and large, Schlesinger's experts, toting notebooks filled with facts and figures. And the President's standby gasoline tax and rebate plan for high-mileage cars were killed, his tax proposal for "gas guzzlers" weakened.

"A lot of them were policy people, but when you get down to the short strokes you need pure political people," one White House aide said. "Some of them had never been to a (bill) markup before."

By early last week, by what was called a "consensus" decision of Moore, Jordan and others, the White House had its political operatives in place where they were needed.

One result of the improved performance of last week is that Moore's standing, never in doubt in the White House, has risen even higher.The congressional relations chief was the subject of early critism from Capitol Hill, but his old friends from Georgia, including the President, closed ranks around him. Now they feel vindicated, and more important, respect for Moore and his men in Congress appears to have grown measurably.

White House officials now concede other mistakes and shortcomings that may have added unnecessarily to their early problems.There was at the beginning a certain naivete about congressional relations. There was initial resistance, perhaps from some of the intense junior White House aides who appear to take themselves and their positions so seriously, to some of the more mundane aspects of it all.

"People don't question us anymore, like about having a picture taken with the President and a congressman with some child from his district," one White House lobbyist said. "Before, some people would say that's not important, that's no way for the President of the United States to spend his time. Well, what may have been important is that the guy may be a swing vote on something we really want."

There have been serious problems, in the view of White House officials, with the Cabinet. The President has sung the praises of "Cabinet government," pledging not to try to run the government from the White House, but now some of his aides believe there has been too much of that. There was little coordination from the White House and too often Cabinet secretaries pursued their own goals with little thought of how their actions might affect the administration elsewhere.

"Now," said a senior White House official, "there is a realization that if the President takes his lumps on energy it sure won't help them in their area."

And there have been even more serious problems with patronage, a major source of unhappiness among congressional Democrats. The President turned over hiring for the most part to the Cabinet secretaries and they in turn failed to satisfy the perhaps unrealistically high expectations of Democrats in Congress after eight years of Republican rule.

"We didn't have as much control as we should," one Carter aide said. "That's where the Cabinet form of government doesn't pay off."

In fact, it went beyond that. One White House official estimated that at least 50 regional government jobs have remained filled with Republican holdovers because the Cabinet and the staff of White House Cabinet secretary Jack Watson have been studying whether to continue the entire regional system.

"It was stupid," he said. "All we've done is left Republicans in place for four or five months, angered the Congress and then reached the conclusion that we should continue the regional system."

By and large, White House aides say these and other problems and mistakes have been ironed out. It has, they concede, been a learning process for all, including the President. There is less talk now of Carter "going directly to the people" (over the heads of Congress) and more realization that even a popular President cannot automatically translate that popularity into the right kind of vote in a congressional committee.

But just as the President's congressional relations appeared to go from bad to good in just a few days, so it is risky to predict what the future holds in this slightly unorthodox relationship among Democrats. Carter has established among Democrats. Carter has established a good relationship with House Speaker O'Neill (D-Mass.) and Senate Majority Leader Robert Byrd (D-W. Va.), both of whom are credited by Carter aides with yeoman service on behalf of the President.

But for all that, and for all the public talk of harmony over the last week, there are influential people in the White House who still welcome a presidential veto - as "a clear reminder to them that we've got the power of the presidency and are able and willing to use them," as one of them said.

The truth probably is that Carter doesn't care much for Congress and will never be personally close to many of its members. But the more important truth may be that he is an intensely ambitious man and, as his aides say repeatedly, "he is not dumb."

"He sees an institution that he's got to deal with for the next four years and if he is not successful in dealing with it he won't be successful as President," one of them said. "It's like during the campaign - the getting up at 5 in the morning and working your tail off until 10 or 12. It's what's got to be done. It just isn't always pleasant.