When Mayor Marion Barry four years ago hired Elijah B. Rogers as his city administrator, the two strong-willed men erected an invisible wall that separated their offices on the fifth floor of the District Building. The wall informally defined where politics was to leave off and professional management techniques were to pick up in running the government.

From his end of the long fifth-floor corridor, Barry freely admitted that "everything I do is political," while at the opposite end, Rogers, the manager, always told reporters, "I don't get involved in politics."

But the wall soon began to crumble as the city's looming budget and bureaucratic problems, which became grist for the mayor's critics, inevitably drew Rogers into the political fray.

He increasingly was called upon to direct the city's resources to douse political controversies, such as the uproar on Capitol Hill over the city's early problems in managing its cash flow and budget and the widespread complaints about the city's error-prone water billing system.

Now, as Barry begins his second term with a strong mandate from the voters and as Rogers prepares to leave the administration, the remnants of that wall have been swept away in a major reorganization.

Barry says the plan will streamline and improve the maturing city government. But it also heralds the start of a much more political administration. That has some of the mayor's critics and even some supporters apprehensive.

For one thing, they are bothered by Barry's blatant insistence upon blind loyalty from city employes. Since the election the mayor has clamped down hard on employes he believed spoke out of turn or released what he considered inaccurate information.

Barry's frequent quips to reporters that disloyal city employes "will be on the unemployment line" are not lost on increasingly uptight employes, who are reluctant to speak out or divulge information that might prove embarrassing to the administration.

Moreover, there is some concern the mayor's reorganization plan adds a highly political luster to the daily operations of the city by transferring responsibility for city departments and agencies from the office of the city administrator to three new deputy mayors who report directly to Barry.

Until he departs in May, Rogers will serve as deputy mayor for operations, overseeing the vast majority of city agencies. His replacement has not been announced. Alphonse G. Hill, the former city controller, became deputy mayor for finance. Ivanhoe Donaldson, Barry's top political adviser and former campaign manager, was named deputy mayor for economic development.

For some, Donaldson's appointment underscores the new political atmosphere in the District Building. No one questions Donaldson's intelligence, his political and business savvy or his talent for getting a job done. But some city officials and council members say privately it just doesn't look right for Donaldson to go from handling Barry's record $1.3 million reelection campaign to taking charge of negotiating business deals involving millions of dollars in city programs and development rights.

Inevitably, they say, questions will be raised about the extent to which Donaldson will allow the mayor's political interests to affect agreements he negotiates in his new job.

Barry and Donaldson both say this is a phony issue and.

"I'm about the straightest shooter I know," said Donaldson, who helped oversee the city's cash management system and directed the Department of Employment Services during Barry's first term. "My mission is to help the city, and I intend to do that . . . . I know how to do it, and I've got the experience to do it."

A high-ranking city official said the city's economic development czar has to be a politically astute person who can speak for the mayor in dealing with powerful business interests. In assigning Donaldson that role, the official said, the mayor clearly shows that stimulating economic development and creating jobs are his top priority.

In an interview last week, Rogers downplayed the risks involved in Barry's new reorganization plan. He said that in key slots, such as deputy mayor for operations, Barry inevitably will put experience in city management above political considerations.

"If you get the wrong people in there, obviously you're going to have a problem," he added. "But that's true even with a city administrator system."