Disbelief, a few cynical snickers and general bemusement greeted announcements last year that the Carter administration would attempt to push civil service reform through Congress, and among the doubters were some of Carter's top officials.

"Until early this year, the White House didn't really think the bill had a chance of passing this session," said Si Lazarus of the White House domestic policy staff. "Almost everybody figured we'd give it a big sendoff, give it some visibility, see whether maybe we could get it through one House and then try again next year."

The bill's passage last week by Congress confounded several veteran observers who were betting that narrow but intense opposition from a few interest groups - federal employes, their unions, veterans groups and their respective allies in Congress - would be sufficient to kill it prior to any committee action.

As a plan designed to improve the process of government itself, the legislation is unprecedented not only in its sweeping scope but in its fleet rites of passage according to Dwight Ink, a widely respected bureaucracy who has served under six presidents. Now at American University, he helped prepare the civil service reform plan at Carter's invitation.

Other such projects began with the notorious process known as a government study, which always took two or three years all by itself. In this case, Ink noted that initial phase was completed with rare dispatch in three or four months late last year.

The bill owes its swift passage to the apparent public mood in its favor, which in turn buoyed several other key factors - bipartisan support in both houses of Congress. President Carter's own persistence, shrewd management of the issue by Civil Service Commissioner Alan K. (Scotty) Campbell and a crucial compromise with organized labor.

The process produced not only a bill for the administration but also by numerous accounts, a valuable learning experience in the administration's often painful education on how to deal with Congress.

At the White House signing ceremony for the bill yesterday, Campbell said the occasion put the lie to accusations that the White House lobbying team was inept.

"Naive we may have been," he said. "But we are here today."

The Senate, House and White House teams differed sharply from time to time on the proper strategy for the bill, and each now claims credit for quarterbacking the winning plays.

Campbell, 55, a genial, slightly rumpled former professor who likes to arrive for work at 6:30 a.m. had given the White House early encouragment that the bill could be passed during this session, Lazarus said. "But Scotty was unknown then. His stature has increased rather dramatically since then."

Campbell has won broad praise as the chief administration architect of a spectrum of groups that impressed key members of Congress and made the plan a "motherhood" issue, according to Senate sources. With such divergent groups as the Business Rountable Common Cause, Ralph Nader and - to some extent - organized labor supporting the thrust of the program, it became practically irresistible.

The centerpiece of the coalition was the shakiest. It was a labor compromise worked out agonizingly and secured only at the 11th hour under the direction of Rep. Morris K. Udall (D-Ariz), who managed the bill on the House side.

The compromise writes into law rules governing federal labor-management practices, which previously were revocable by presidential fiat. The compromise also gave union leaders a slightly expanded scope of collective bargaining and other long-sought changes.

In the Senate, the early enthusiasm of Sen. Ribicoff (D-Conn.) and Charles Percy (R-Ill.), both of whom had more credibility last year than newcomer Campbell, gave the bill the momentum it needed, according to administration and other sources.

Percy, who held several field hearings on the issue in Illinois, said he saw the bill as a chance to restore the pride and raise productivity of federal workers by introducing some distinction between the good worker and the poor one.

If executive branch employes did a better job, the Senate staff wouldn't have to be so big," in order to clear up constituents' constant problems involving bureaucratic foulups, Percy said.

The major stumbling block for the program was the House Post Office and Civil Service Committee, a stronghold for allies of federal employe unions and bureaucratic interests who opposed the management-oriented bill because it threatened to end some of their long-held job protections.

Udall, William Ford (D-Mich.) and ranking committee Republican Edward Derwinski (III) are credited with superior performances. They maneuvered the bill past opposing committee members such as Herbert Harris (D-Va.) and Gladys Spellman (D-Md.) who represent suburban Washington government workers, and Rep. William Clay (D-Mo.), a maverick labor ally who almost killed the bill by holding out for far more than ever organized labor was seeking in concessions.

The situation in the House committee nearly "blew up in our faces" several times, Campbell said, adding that as recently as early last month, the administration was prepared to withdraw the legislation entirely rather than accede to the more extreme demands of Clay and some independent union leaders.

"We pointed out to them that, if that happened, the concessions we had already agree to would die with the rest of the bill," Campbell said.

It was Campbell who first convinced the White House team about the wisdom of conceding something to organized labor in order either to win its support or at least to neutralize its organized labor in order either to win cording to administration officials.

But powerful forces within the administration were against almost any concessions to labor. Carter himself felt strongly that he could not give the unions "undue authority" over the running of the government, aides said.

The Defense Department reportedly was adamantly against such horse trading. As the largest federal agency, with nearly half of the federal civilian work force, the Defense Department is "particulary sensitive" on the subject of labor-management relations, as one source put it.

As it turned out, an old friend of Campbell from his days in academia was in position a key role in solving that problem. Campbell, an expert in public administration, is a former dean of the Maxwell School of Citizenship and Public Affairs at Syracuse secretary of Defense for manpower, had studied there.

Estimates are that about 250 of Campbell's former students were salted around the federal government and related organizations when he arrived here.

Campbell and White, among others, spent long hours working out how far they could move toward the unions and finally sent a unanimous recommendation to Carter that he move forward on the bill with the understanding there would be some form of a labor compromise.

If the Defense Department had not endorsed that recommendation, according to Campbell and others, the president almost certainly would not have given the go-ahead on the go-ahead on the entire project.

Last week, with an enthusiastic tribute from Campbell, White was appointed deputy director of the Office of Management and Budget.

Campbell also was able to call on other members of the New York congressional delegation with whom he had been in contact while in the state.

Sources on both the House and Senate sides roll their eyes skyward as they recall various blunders they attribute to the White House lobbying task force. "But they got better as they went along," one source said.

At one point in the negotiations with labor allies in the House, Udall "sort of lectured the president" on the strategy he felt was needed, according to a White House aide.

Carter "sat there and took it all in, and then 30 minutes later he sent word to all of us to 'follow Mo,'" the aide said.

Campbell, accustomed to being the teacher, said he has gained considerable political education himself in recent months, much of it from Udall. "Mo taught me when to make a move and when to hold back. I've learned that politics is more than just having the votes," he said.

"I've been accused by some of my colleagues of trying naively to change iron laws of bureaucracy with mere legislation," Campbell observed wryly earlier this year.

"Well, we're taking all the right steps in pushing this, an open process, informing Congress, talking to the appropriate interest groups, almost a textbook case. We've made a few mistakes, but" - he threw up his hands - "if this doesn't work, I don't know what will."