The dramatic job switch proposed this week in which principal members of the Reagan administration's supporting cast would change roles is characteristic of a long series of staff shake-ups that seem to have barely affected the performance of the principal player.

Throughout a political career now approaching two decades, Ronald Reagan has been remarkably distanced from the comings and goings of his staff. He also has displayed a singular ability to follow his own course after consenting to staff changes that seem at first glance to be harbingers of a new direction.

"I don't think Ronald Reagan is going to change his habits because he has a new chief of staff -- if he feels that chief of staff is performing," Treasury Secretary Donald T. Regan said Tuesday in an interview in his office after the announcement that he and White House chief of staff James A. Baker III would be swapping jobs.

What was unsaid in Regan's statement but well understood is that the president isn't going to change his habits in any case. Despite his reputation for geniality, Reagan has shown during a series of political campaigns, eight years as governor of California and four as president that he would rather change his staff than his way of operating.

"He is a very secure man," said Edward J. Rollins, his 1984 campaign director. "He doesn't feel his presidency succeeds or falls on the basis of the people around him. It succeeds or fails on his own actions."

Reagan is tolerant to what even some supporters consider a fault in retaining embattled Cabinet members, such as Labor Secretary Raymond J. Donovan. But it is a different story on his staff, where over 19 years he has dismissed or allowed to quit such close advisers as Michael K. Deaver, William P. Clark, Edward Meese III, Stuart K. Spencer, Lyn Nofziger and John P. Sears.

All except Sears, fired after Reagan's victory in the 1980 New Hampshire primary, came back to work for Reagan. Deaver, now White House deputy chief of staff, became his closest aide.

But when Reagan was asked Tuesday, in an interview with The Dallas Morning News, about the departure of Deaver and others in his entourage, he replied that he could "not expect them to contract in for the run of the show."

This distance even from those closest to him has been a hallmark of Reagan's political style. On the one hand, Reagan delegates so much that his subordinates often seem to govern in his name. On the other, no aide is indispensable in Reagan's eyes and all are seen by him as advancing his agenda.

"The true believer in the White House is sitting right here in the Oval Office," Reagan said in the Tuesday interview. "And no has been whittling at me or trying to change my philosophy since I've been here."

Reagan went on to praise Regan for his loyalty and to take a swipe at critics on the right who say he is drifting from his conservative principles.

"Sometimes I wonder if some of those very vocal conservatives are really conservatives in conservatives' eyes," Reagan said. "I know they're not in mine."

It was typical of the president to be one of the last to know about the Baker-Regan job switch. He said in his interview Tuesday that when Regan suggested it to him he thought it was "a great idea" and preferable to either man returning to private life.

At a time of staff disarray under Gov. Reagan in 1967, Clark took over as executive secretary, the chief of staff's job, after the proposal had been approved by other aides. When Clark left for a judgeship in 1968, he and Meese agreed that Meese should be the successor before the matter was brought to Reagan.

The pattern continued in the Reagan presidency. Deaver and Clark, then allies, agreed that Clark should become the president's national security affairs adviser before they raised the issue with Reagan. When Clark left to fill the vacancy created by James G. Watt's resignation at the Interior Department, Baker and Deaver worked out a plan making Baker the national security adviser and Deaver chief of staff.

But conservatives, led by Clark, Meese and CIA Director William J. Casey, rallied against this appointment and persuaded Reagan to cancel the plan. He remained distanced from the maneuverings and never acknowledged them publicly.

One consequence of Reagan's seeming separation from staff decisions is that he rarely is blamed when things go wrong or when key members of his staff come under fire. Casey and Baker were bruised by a long, inconclusive investigation into how the 1980 Reagan campaign obtained some of President Jimmy Carter's debate briefing books, but Reagan was scarcely touched by it and he never summoned either aide to resolve the matter.

In the comings and goings of staff members, Nancy Reagan always has played a quietly active role, notably in the firing of Sears and the original hiring of Baker as chief of staff.

But Reagan may be less removed from power struggles in his official family and more aware of the limitations of various aides than he reveals. One intimate says the president has "an intuitive understanding" of when change is necessary and acts on this intuition.

Reagan's relationship with Meese demonstrates this insight. In 1980 Reagan fired Sears rather than get rid of Meese. But when Nancy Reagan, Deaver and Spencer came to him and said Baker would be a better manager as chief of staff than Meese, they found the president to be a willing listener.

According to inside accounts, Reagan expressed agreement with criticisms of Meese's managerial skills and quickly decided that Baker should be chief of staff. At the same time Reagan made it clear that he valued Meese's counsel and wanted him in the White House.

When Attorney General William French Smith told Reagan he wanted to return to California, Meese was the president's first and only choice to replace him.

The latest proposed staff switch also may reflect a personal choice, although Reagan merely consented to it. It is well known in the administration's inner councils that the president is comfortable with Regan, and Baker and Deaver know better than to make a recommendation that makes Reagan uncomfortable.

"Reagan is Reagan," Rollins said. "As Regan will find out, Reagan has strong feelings on things -- and how to get to those things isn't dependent on staff options."