In deciding on a dramatic exercise in personal diplomacy with his trip to the Middle East this week, President Carter is taking perhaps the biggest political gamble of his presidency.

Carter is returning, symbolically, to the scene of his greatest triumph in office -- the Camp David accords of last September -- against the backdrop of a new wave of criticism of his performance that now centers on his conduct of foreign policy.

If the trip succeeds in achieving a breakthrough toward the long sought Egyptian-Israeli peace treaty, it could give the president the kind of boost in public esteem and confidence that followed the Sunday night television spectacular at the climax of the Camp David summit. He needs such a boost now at least as much as he did then.

But a failure could not be glossed over. From the beginning of the Middle East peace process, it has been assumed, in the White House and elsewhere, that Carter would at least get credit for trying to solve what has been an unsolvable problem.

That is probably still true. But by traveling to the Middle East himself, the president is placing his personal prestige on the line at precisely the moment that his foreign policy successes and failures -- as opposed to his intentions -- have come under the heaviest fire.

"Whether it's fair or not, people in this country judge a president on results," one presidential aide acknowledged in considering the risk the president is taking.

White House aides, reluctant to discuss political consequences and insistent that political considerations played no role in the president's decision to leave Wednesday for Cairo and Jerusalem, nonetheless concede that the stakers are high for Carter.

"It's a gamble," one official said yesterday shortly after the trip was announced. "It raises expectations, focuses attention on this act at this time. The very fact that he is going highlights it. If the trip does not result in success, expectations will fall even further than they might have otherwise.

"Politically," the official added, "the safest thing would have been for Carter to come out of the meeting with [Israeli Prime Minister Menachem] Being and put a little distance between himself and the problem -- a little distance between himself and Begin and [Egyptian President Anwar] Sadat. I think the downside is great."

Another official said: "He's always been willing to take personal and political risks. He did it at the first Camp David, but this is certainly one of the biggest risks he's ever taken. The consequences of failure are most serious for the Middle East, but he's clearly putting his prestige on the line."

The risks in the venture for Carter are extremely high not only because of his decision to conduct it personally -- "you don't have to get your hands dirty over there, you could try to run it from here," as one administration official said -- but because there are no illusions in the White House that this will be the last chance to salvage a treaty from the Camp David accords.

Acknowledging this, one senior official said, "That was clearly going to be the case anyway. The question is would we allow it to fall apart by itself or take one last dramatic shot."

"The feeling around here is that time is not on our side," another official said in explaining a decision Carter apparently made with little if any consultation with aides."The feeling is that Sadat is neither fish nor fowl. He doesn't have a peace treaty and he is not any longer a leader of the Arab world. He can't remain like that forever."

It is doubtful, after all that has happened and is likely to happen in the next few days, that Carter will ever be able to put much distance between himself and Sadat and Begin. By his own frequent testimony, he has devoted more time to the Middle East peace process than to any other single issue. He is indelibly identified with its outcome, whatever that may be. His aides doubt he has given that much thought.

"Carter is a strainge sort of fellow," one of them said. "He's not giving politics any consideration now on anything. That's the way he is and you've got to be true to youself.... It's both a great political attribute and a weakness."

"Yes, it's personal gamble for the president," another official said last night. "If it does not succeed, the failure will be laid at his doorstep. But he felt that nothing short of his personal involvement would work."