President Carter, as has become apparent, has adopted a new public style since his "domestic summit conference" at Camp David. Whether he is addressing a national television audience or a group of reporters over lunch, the president is trying to be more forceful, to project the image of a man in charge.

In the last week, it also has become apparent that one of Carter's closest aides, a man who in many ways publicly mirrors the mood of the White House, is trying to do something of the same.

For the last several days, presidential press secretary Jody Powell has been doing his best to repress his naturally competitive and sometimes combative personality in his daily briefings of White House reporters.

Powell, it often has seemed, enjoys nothing more than verbal combat with the president's enemies, real or perceived. Naturally quick-witted and skilled in parrying questions, he seldom passed up a chance for a sarcastic or otherwise deflating retort to a question he didn't like. Sometimes, he was just nasty.

But not last week. Instead, Powell appeared at the daily briefing prepared with long answers to questions he anticipated, pushing Carter's point of view. When opportunities for the quick retort he specializes in inevitably arose, he passed them up for the most part.

The "new" Powell demeanor has not come about entirely by accident. During the Camp David discussions, some of Carter's visitors told him his longtime press secretary and close aide seemed overwrought, too quick to lose his temper and to look for fights with the press. The president met with Powell at the presidential retreat, passing on the perception that the press secretary's sometimes short-tempered ways were not doing any good.

In an interview last week, Powell confirmed that he deliberately has sought to adjust his style to smooth relations with the White House press corps.

The month of July, Powell noted, with its abrupt cancellation of Carter's energy speech, the mysterious comings and going at Camp David and the purge of the Cabinet, produced a fair amount of turmoil in the press corps."

"I thought it was to everybody's benefit to get things back to normal," he said. "I thought I ought not to do anything that unintentionally would rub things rawer, rub the scabs off. It was time to spread a little oil on the waters."

Powell spent the entire 10-day period of the "domestic summit conference" at Camp David, out of touch with his constituents, the White House press corps. But he occasionally briefed reporters on the Camp David talks, using a method that reduced the routine of the daily White House briefing to its ultimate absurdity.

Every day or so during the summit, with no particular pattern, reporters were called to the White House in late afternoon. They gathered in Powell's office, filling the furniture and sitting on the floor.

On Powell's desk is a loudspeaker connected to a telephone. At the appointed hour, Powell called his own office and, his voice amplified by the loudspeaker, reported on the day's activities at Camp David.

The press secretary's deputy, Rex Granum, sat behind Powell's desk and relayed questions. The voice from the mountaintop then replied.

The exercise tended to fray nerves both in White House offices and in the press room. Powell said he was aware of this, as well as of the suspicions - fed by such actions as the president's announced intention to cut back on Washington press conferences - that the Carter White House was about to declare war on the Washington press corps.

In this atmosphere, Powell said, "It was my view that if I had been my normal self there was a reasonable likelihood that some would not take it as just Powell jabbing people like he always does, but to put it in another context" - possibly reading dark motives into his behavior.

That perception, as much as his chat with Carter at Camp David, resulted in the emergence of the more serious and less sarcastic Jody Powell, he said.

And how long can reporters expect this to last? Powell was asked.

"I don't know," he replied. "The other thing is I've had a toothache for about two weeks and finally got it fixed. That might have more to do with it." CAPTION: Pictures 1 and 2, no caption, By Harry Naltchayan - The Washington Post