The Carter administration maintained an atmosphere of outward calm and confidence yesterday while awaiting the final political judgment on the aborted Iranian hostage rescue mission and the protest resignation of Secretary of State Cyrus Vance.

Even as ripples of concern spread through Congress and Embassy Row at the departure of the man Carter had picked to run the Nation's diplomacy because he was a "level-headed, competent . . . superb adviser and negotiator," White House aides were heartened by evidence that public opinion -- so far at least -- appears to be sticking with the president.

"The reaction to the failure of the mission has been substantially less critical than I expected," said one West Wing aide. "My guess is that a week from now, we will be onto other subjects."

However, the reaction in Congress to Vance's resignation made that prophecy appear hazardous. Expressions of regret came from leading foreign policy spokesman of both parties, with men of such varying views as Sen. George S. McGovern (D-S.D.) and Rep. Edward J. Derinski (R-Ill.) saying his departure would weaken the administration.

"He was the wisest man in the cabinet," McGovern said. "I worry about what this does."

"From the standpoint of world perception, this will be another black eye for President Carter," Derwinski added. "[It has] the appearance of a key adviser leaving a sinking ship."

Their comments found an echo in the worried tone of statements from America's allies, and the issue seems certain to remain alive -- at least on Capitol Hill. Confirmation hearings on Vance's successor will publicize the administration's internal divisions on foreign policy and congressional investigations on the failure of the aerial rescue mission in Iran will open Carter's decision-making to second-guessing.

But for now, at least, the White House was cheered by a national poll showing strong support for the rescue attempt and equally strong public rejection of the contention from some of the president's critics that selfish political motives led him to approve the venture that ended in the deaths of eight Americans in the Iranian desert.

Carter himself moved to sustain that support by becoming a more visible national leadership symbol than he has been since the start of the hostage crisis almost six months ago.

He left the Washington area for the first time in 182 days yesterday to visit five wounded survivors of the mission in their hospital beds in Texas. Tonight, he will hold a prime-time (9 p.m.) news conference to set forth his rationale for the decision and perhaps to suggest the next steps he will take to try to free the 53 U.S. hostages.

For the moment, Carter was being helped even by those who had doubts about his actions. While one high official of the president's reelection campaign complained that "Cy has a helluva sense of timing," the secretary took two steps to limit the immediate damage his resignation caused the administration: He gave no public hint of the basis for his disagreement with Carter's decision to order the rescue effort, and he urged his top State Department associates to remain in their jobs to help Acting Secretary of State Warren Christopher.

As a result, one senior White House official said, "we felt no need" to take special measures to "keep others from following Vance over the side." The secretary's resignation and the Iranian mission's failure were major topics at yesterday's senior staff meeting, the source said, "but there was no sense of undue concern."

One reason for the calm was the indication of what another side called "pretty damn strong public support" for Carter's action.

An Associated Press-NBC News poll, taken Friday and Saturday, found 66 percent approval of the rescue attempt and only 24 percent disapproval.Two-thirds of the 1,603 people interviewed said they thought the attempt should have been made earlier and 54 percent said a similar mission should be tried again.

It also cheered the White House that 65 percent of those polled rejected the suggestion that the failure of the rescue mission was "one more example of President Carter's inability to handle the job of the presidency." And it was good political news that 61 percent said Carter was trying to do what looks best for the country, while only 23 percent attributed his actions to his reelection campaign.

The only disquieting note, from the president's viewpoint, was that the overall rating on his handling of the hostage crisis fell from 47-to-40 positive in late March to a 42-to-46 negative in the latest poll. Other surveys have shown a close correlation between voters' rating of Carter's handling of the hostage crisis and their decision on whether to support him for renomination and reelection.

A weekend poll by the Gallup organization also suggested that a great many Americans are holding back in making judgments on Carter after the failed rescue attempt.

In interviews with 1,000 people Saturday and Sunday, the Gallup firm found virtually no change, for example, in voter preference between Carter and Ronald Reagan from that expressed before the aborted raid. Carter led Reagan by 47 to 43 over the weekend; he led by 49 to 43 in earlier polling from April 11 to 14.

In addition, the new poll found Carter's "approval rating" about the same as it had been. Forty-three percent of those interviewed expressed approval of the way Carter is handling his job as president, compared to 39 percent earlier in the month.

However, the number expressing disapproval declined by 11 percent -- leading Gallup analysts to believe that many people are awaiting further developments before drawing conclusions that could affect the president's political future.

Direct comment from Carter's rivals for the presidency remained muted yesterday. Democratic challenger Edward M. Kennedy said in Mexico City he was "saddened" by Vance's departure and said the development made a full investigation of the rescue attempt "even more urgent."

Hinting that he might share Vance's doubts about the mission, Kennedy said that, of all Carter's foreign policy advisers, he had the "greatest respect" for the secretary. "Obviously, he knows far more about the failed military effort in Iran and its possible consequences than the rest of us do. . . . The nation needs to know all the relevant facts that led the secretary of state to take the extraordinary step of resigning."

Republican presidential hopeful George Bush, who gave his unequivocal backing to the rescue effort on Friday, made somewhat conflicting comments on Vance's resignation.

Early in a Houston campaign day, Bush said, "I do have personal respect for Secretary Vance, but I do not agree with his reasons for departing or the rationale. I don't agree with him at all. . . ."

At a later stop, however, Bush referred to the "deep divisions in the administration" and said that rather than "sending out confusing signals to our allies and adversaries. . . . he did the right thing, and I think the president was correct in accepting his resignation."

There was no comment from Republican front-runner Ronald Reagan, but Rep. Thomas B. Evans Jr. (R-Del.), the head of Reagan's congressional advisory panel, said he found the resignation "scary," because Vance was one of the last pros there."

It was chiefly on Capitol Hill that misgivings were expressed about the implications of Vance's resignation, with many of the worried lawmakers saying they saw his departure as a victory for national security adviser Zbigniew Brzezinski.

Sen. Ted Stevens (R-Alaska), the assistant minority leader, said, "We're all going to be sorry to see Vance go. In this crisis, he's been a stabilizing factor." Sen. Claiborne Pell (D-R.I.), ranking member of the Foreign Relations Committee, said, "It could mean a more strident foreign policy and a less steady one." McGovern, another member of the committee, said that if Vance's departure meant "elevating Brzezinski," it would mark a victory for the "confrontational approach."

Perhaps the most gloomy appraisal came from Rep. Jim Leach (R-Iowa), a former Foreign Service officer, who said that Vance's resignation "will be read abroad as evidence of a disintegrating American foreign policy and perhaps a disintegrating administration."