With the 95th Congress finally adjourned, President Carter could look back yesterday on a two-year legislative record that is a mixture of solid achievements a series of White House declared "victories" that fell far short of their original objectives, and some acknowledged setbacks.

But what is beyond dispute is that it is a far better record than was generally thought possible a year or even six months ago.

To get from where he was - for a year Carter's competence in dealing with Congress has been openly questioned while his standing in the polls continued to decline - to where he found himself yesterday required the president to shed some principles and practices he brought with him as the political "outsider" come to Washington.

Among these were his proclaimed devotion to "Cabinet government" with the least possible control by the White House, his determination to hold the size and powers of his staff to a minimum and his reluctance to engage in the give-and-take of trade-offs that is at the heart of the legislative process.

White House officials counted among the achievements of the last six months passage of the Panama Canal treaties, the Middle East arms sale package, the lifting of the Turkish arms embargo, airline deregulation legislation, several parts of the president's urban policy and the bill to overhaul the civil service system.

In other cases, Carter fell short of some of his ambitious goals, but could still claim to have made progress. Congress enacted several parts of the administration's national energy policy, including the controversial measure to deregulate the price of natural gas, but what finally passed was far from what the president initially advocated. At the last minute, Congress also enacted a tax cut measure, but without most of the "reforms" Carter sought. The Humphrey-Hawkins "full-employment" bill that has gone to the White House for Carter's signature is a shell of the original proposal.

The setbacks included the failure to eact welfare and labor law "reform" bills and the hospital cost-containment legislation or to create a Department of Education.

But even with the setbacks and all the compromises Carter was forced to made, the end-of-the session record clearly represented a sharp rebound from the low points of last winter and spring, when it seemed possible that most of the president's legislative goals would elude him.

The scenerio of the turnabout might easily be entitled "Three Days in April," for it involved two unrelated events last April that White House officials point to as the beginning of the upswing.

The first occurred April 16 and 17 when Carter summoned his Cabinet and senior White House official, that "the shakedown cruise is over." The meeting marked the president's acknowledgment that what had gone before had not gone well, and from it came a shake-up of White House operations that would have its impact in the months ahead.

The second event occurred April 18 when the Senate approved the second Panama Canal treaty, climaxing what Carter has called his most difficult undertaking as president. That victory gave White House aides a badly needed morale boost and, more importantly, provided them with a prototype for dealing with Congress in the future.

Beginning with these events, the evolution in Carter's approach to Capitol Hill accelerated rapidly with clear benefits to the administration by the end of the 95th Congress. The changes included:

The beefing up of the White House staff both in terms of numbers and ability to function in the world of Washington politics:

Last year, the White House made do with four lobbyists on Capitol Hill. By the end of the 95th Congress, there were seven, and they were backed by an enlarged support staff.

There was a time, one official recalled, when Carter's congressional relations aides could not obtain a government car to travel to Capitol Hill at night. It was part of the austere "nonimperial" presidency that Carter promised. Now those days are over and White aides seek ways to do traditional favors for members of Congress that might mean a vote somewhere down the line.

In addition to more lobbyists, Anne Wexler, a former undersecretary of commerce, was brought into the White House to begin the first serious attempt to rally interest groups behind administration goals, and Gerald Rafshoon, Carter's 1976 advertising chief, took over the planning of media campaigns to accompany the Capitol Hill lobbying.

The White House took over control of administration efforts on the president's top-priority legislative objectives:

Carter came to the White House proclaiming that his would be a "cabinet government," not one run from the White House. But in the canal treaties effort, directed entirely from the White House, the president and his aides learned the value of central control and coordination.

Since then, the same basic technique, establishing a "task force" in the White House to issue orders to administration officials and monitor progress, has been used on a number of key issues, including the successful defenses of Carter' vetoes of the military and public works appropriations bills.

Finally, Carter the "outsider" learned to play a more traditional insider's role, in the end, according to some aides, relishing the wheeling and dealing with members of Congress.

During much of his first year in office, the president buried himself in the details of government, pouring over an endless stream of memos and other papers. By the closing weeks of the 95th Congress, he was reading less and talking more, placing as many as 30 telephone calls a day to Capitol Hill and seeing dozens of members of Congress in his office.

In the course of this, Carter cut his deals with members - even his own aides don't deny this, conceding that the president became more "flexible."

One official,describing the exprience of Carter and his inner circle of advisers with the 95th Congress, said they all "grew up" in the process.

"They learned that they could not depend on the value of a decision innately - that Jimmy Carter could not just look at an issue, study it and make the right decision and then expect that it would be automatically ratified." he said.