Washington — President Carter's appointment of Sen. Edmund S. Muskie (D) of Maine as secretary of state has given the nation's professional diplomats a much-needed boost in morale.
Most officials at the State Department seemed to welcome the appointment, in part because Senator Muskie is expected to be the sort of man who will stand up to Zbigniew Brzezinski, the President's national security adviser.
But there is more to it than that. A number of State Department professionals said they are happy with the Muskie appointment because the senator, in their view:
* Is a political "moderate," at the center of the political spectrum, without any ideological liabilities.
* Will be a more articulate and forceful foreign policy spokesman than the outgoing secretary of state, Cyrus Vance, ever was --or even tried to be.
* Will be able to do the best possible job of selling the administration's foreign policy to an independent-minded Congress.
The administration has had difficulty getting what it considers to be crucial aid requests through the budget-conscious Congress. On almost every major foreign policy issue, from the SALT II and Panama Canal treaties to its policy toward southern Africa, the administration has had to fight hard battles on Capitol Hill.
There is even some feeling that if President Carter were re-elected -- and if Mr. Muskie then stayed on as secretary -- he would be able to halt a tendency for power to flow away from the State Department to other government institutions, such as the Commerce and Treasury Departments.
"When we look at Senator Muskie's contacts and his bureaucratic strengths, we see the potential for someone who can turn this erosion around," said Ken Bleakley, president of the American Foreign Service Association, which represents 11,000 persons working for the State Department and the Agency for International Development.
About the only negative comment or note of caution heard from most Foreign Service officers was that Senator Muskie has a reputation for being harsh with his subordinates in times of stress. But opposition to the appointment, at the State Department at least, was hard to find.
"You have a great deal of enthusiasm for the fact that we'll have an 'up front' secretary of state who can speak out on some of the difficult issues we face," said one of the 14 assistant secretaries of state with whom the senator will work when he joins the department.
Many State Department officials had been guessing that either Warren Christopher, the deputy secretary of state, or Sol Linowitz, President Carter's chief Middle East negotiator, would be appointed to replace Secretary Vance. Many would have approved the appointment of either man. The announcement of the Muskie appointment came as a surprise.
But, upon reflection, a number of officials said they thought Mr. Christopher , a self-effacing lawyer, might not have been forceful enough for the job. It was noted that in the course of a mission to offer aid to Pakistan last January in the wake of the Soviet invasion of Afghanistan, Mr. Christopher was overshadowed by Mr. Brzezinski.
During the visit to Pakistan, Mr. Brzezinski offended State Department professionals by dramatizing his attitude toward the Soviet Union through the brandishing of an automatic rifle.
Mr. Muskie will control Mr. Brzezinski in the White House, said one State Department official following the announcement of the appointment April 29. "He'll check whatever danger there is of our sliding down that slippery slope toward war."
"It's been said that Vance fought his battles with Brzezinski under the Marquis-of-Queensbury rules," the official continued. "Brzezinski's a street fighter. . . . But if Muskie has to fight back, I suspect he'll fight under Jack-the-Ripper rules."
This official added that he likes Senator Muskie because "he has liberal credentials but isn't out in left field."
"Muskie dislikes labels like 'hawk' or 'dove,'" the official said. "He considers labels a substitute for thought."