A Carter comeback is now in full swing. But not, as some imagine, because of the afterflow of the Camp David summit.

On the contrary, a common factor underlies the success at the summit and in dealing with the Russians and the Congress more recently. In all cases the president adjusted his position to the lesson of events.

Mr. Carter came to office pressing for a comprehensive settlement to be worked out between Israel and the Arabs at a Geneva conference with the Russians. But Anwar Sadat, rather than being thrown in with the Russians and the most recalcitrant Arabs, preferred to cut his own deal with the Israelis. At Camp David, President Carter abandoned the comprehensive settlement, and acted as a broker for what comes close to being a separate peace.

In dealing with the Russians, Mr. Carter started off with an emphasis on human rights, which gave great importance to the dissidents in the Soviet Union. He then surfaced proposals that went far beyond the second stage strategic arms limitation treaty (or SALT II) guidelines approved by Leonid Brezhnev and President Ford at their Vladivostok meeting in 1974. Carter then tried to make agreement on SALT conditional on good Soviet behavior in Africa.

In response, the Russians accused the president - through attacks on his special assistant for national security, Zbigniew Brzezinski - of trying to sabotage SALT in order to appease American hardliners. To drive home the lesson that they would not make concessions on internal policy in order to get an accord on SALT, they staged highly public trials of Russian dissidents, U.S. newspapermen and an American businessman.

Carter reverted to discreet and indirect diplomacy to have charges dropped against the newsmen and to have the sentence of the American businessman suspended. He toned down Mr. Brezezinski, and allowed Secretary of State Cyrus Vance to emphasize an approach to African affairs that minimized big-power rivalry.

With the lesser subjects thus reduced to their true proportions, it was possible to resume constructive work on the most serious business. Now the prospects are good for a SALT accord at a summit meeting between Presidents Carter and Breznhnev before the end of this year.

As to the Congress, Carter started by proclaiming positions and handing down programs without reference to the interests of the senators and congressmen. He ran into trouble at the start when his "hit list" of wasteful water projects forged an anti-Carter alliance of Democrats from the South and West and Republicans. The anti-Carter alliance had a field day with the president's energy program.

The program he sent up emphasized conservation of energy on the ground that the world was rapidly running out of oil and natural gas. What emerged from the House and the Senate and their conference committee was a program that emphasized more production of oil and natural gas to be achieved by the incentive of higher prices.

Carter accepted the compromise, and then went to work with Majority Leader Robert Byrd to push it through the Senate. A strenuous lobbying campaign brought the pressure of interest groups to bear on dozens of senators. In addition, Carter put on the line the presidency and the promise he had made to cut oil imports at the Bonn summit meeting of allied leaders last July. A week ago last Wednesday he and Majority Leader Byrd won big in the Senate.

Roughly the same conditions apply to the successful veto of the public works bill and its water projects last week. Intense White House lobbying for support of a veto got under way in early September and continued unabated through last Wednesday. This time Carter set his case against the water projects in an argument he had previously disdained. He claimed they were inflationary, and would weaken the dollar abroad and his hopes of curtailing wage and price hikes here.

The inflation argument was potent. Though Speaker Tip O'Neill and Majority Leader Jim Wright were committed to the bill, the administration stripped away many fiscally conservative Democrats with leadership positions. About 50 fiscally conservative Republicans broke with Minority Leader John Rhodes to sustain the veto.

What all this says is that the Carter comeback is not a matter of luck or the pendulum of affairs. Carter made a series of blunders when he first took office. He began turning around last year, and his stock then dropped very badly because he appeared to be indecisive.

But the process of adjustment now pays off. As long as he continues to learn the lesson of failure, the president can go from success to success.