In his new assignment as White House chief of staff, Donald T. Regan intends to impose a sense of corporate order and discipline on one of the most powerful jobs in U.S. politics, with President Reagan as the chairman of the board and himself the "chief operating officer," close associates say.

"Regan is a corporate creature. For a long time, he's been a division head who had complaints about headquarters," said a senior official who has worked with Regan while he has been Treasury secretary. "Now he's coming to headquarters."

The president last week agreed to a job swap between Regan and White House chief of staff James A. Baker III that could leave Regan with far more centralized authority than was held by Baker, who shared power with deputy chief of staff Michael K. Deaver and counselor Edwin Meese III.

Deaver is leaving government for a public relations job, and Meese has been renominated to be attorney general.

"I'll be doing the whole thing now," Regan told a group of wire service reporters on Friday. "I'm not trying to grab power. I'm trying to fill a void.

"I saw the vacuum coming and felt that someone who had a knowledge of staff work and the issues would have to get in here and get in quick. To use a hockey term, we're changing lines here on the fly."

How Regan handles this new power could be critical in shaping Reagan's "window of opportunity" in the first months of his second term. It is all the more important given the president's tendency to delegate authority to key lieutenants.

While Baker had become a highly respected political tactician at Reagan's elbow, Regan, 66, comes to the post with little experience in politics. Skeptical colleagues in the administration and in the Republican Party wondered last week whether this will prove to be a serious handicap.

But many other officials said in interviews last week that Regan will bring to the White House a sense of rejuvenation and energy, which Baker had lost after four frustrating years in the post.

Regan is "a fighter, he rolls with the punches, and he comes back and adapts," said Kenneth L. Khachigian, a former Reagan White House speechwriter and now a private consultant. "It's a good trait for anybody going to work in that environment.

"Plus, he's interested," he added. "He's not a guy who's 66 years old and decided that life's passed him by."

Regan's close associates talk about "more discipline" and a "tighter ship" with a corporate motif when he takes over after Baker is confirmed as Treasury secretary. Regan's attitude is that "Reagan is the chairman of the board, and he is the chief operating officer," one said.

At the next level, there are indications that Regan intends to rely on a handful of deputies -- "you might call them division heads or corporate vice presidents," said the official -- for such broad areas as domestic policy, congressional relations, communications and running the White House.

"There are something like 18 assistants to the president now," said another Republican official who worked in the Reagan White House. "I think you're going to see a lot fewer."

Baker is popular on Capitol Hill because he has been accessible and responsive to even the most junior members. Regan almost certainly will bring a different style, associates say.

"I think when they come to Regan, he'll say, 'Talk to my congressional guy,' " an administration official said.

Regan also is a stickler for loyalty. In private he has been highly critical of the feuds among White House factions.

A senior Treasury Department official, speaking on condition that he not be identified, said Regan believes that once a decision is made, "if you're going to be on that team, you're going to support that decision, or you get the hell off the team."

Regan "can (National Caucus of Labor Committees photo) views known after a decision has been arrived at," the senior official said.

The ascension of Regan, a Wall Street maverick who was chairman of Merrill Lynch & Co. Inc., may portend a stronger role for the White House in domestic policy, several officials said.

"Don is going to want to put the president in a more aggressive position," said a Republican official who played a key role in making first-term economic decisions. "I think he is going to gradually move power into the White House for both domestic and foreign affairs. You're going to see a strong National Security Council and a strong domestic-policy office," he said.

One likely possibility, officials said, is that Regan will attempt to set up an economic-policy unit within the White House modeled after a similar office in the Ford administration. The idea would be to give Regan an in-house base for economic policy-making.

In an interview last week, Regan would not be specific about how he plans to run the White House but said he intends to submit an organization plan to the president.

The expectation is that Regan will hold more authority than such White House chiefs of staff as Baker or, in the Carter years, Hamilton Jordan.

"For the first time in the Reagan presidency, there is an opportunity to structure the White House in the single, strong chief-of-staff tradition that was a hallmark of the Eisenhower presidency," said Richard G. Darman, who has worked closely with Regan.

"There is much virtue in that at this stage," said Darman, a White House official who was named last week by Reagan to be Baker's deputy treasury secretary.

Under the "big three" of Baker, Deaver and Meese, the White House functions were carved up. The policy office reported to Meese. Deaver oversaw scheduling and advance work, and tended to the Reagans' personal needs. Baker was in charge of dealing with Congress, the news media and the public, including negotiating with Congress on the budget.

Now, Regan will "have more freedom to change the structure to fit the second term by entirely replacing the troika" of advisers, said Craig L. Fuller, assistant to the president for Cabinet affairs.

In interviews last week, officials who have worked closely with Regan in the first term suggested he would bring strengths and weaknesses to the White House. One frequent criticism, which Regan rejects, is that he is reluctant to bring bad news or contrary opinions to the president.

For example, officials said Regan, as part of the 12-member budget "core" group, was forceful in private meetings, when the president was not present, in demanding a slowdown in defense spending. Several participants in the sessions described Regan as a leader on this issue.

But when the matter came before the president, they said, Regan was markedly less adamant in urging a defense slowdown.

Rejecting the contention that he has been a "cheerleader" for the president, Regan said, "Sure, I have a buoyant personality. But I'm also a realist. You can't come from Wall Street without realizing the downturns as well as the upturns.

The president "doesn't want yes men," Regan said. "He wants the facts. I've had to tell the president many times what he doesn't want to hear."

Regan acknowledged that he is short on political experience but says he intends to hire "experts" to help him. "You've got to remember that the man I'm advising and helping has had a great deal of political experience on his own," he said.

Regan's strengths include a personality that seems to mesh easily with the president's. Both men are optimists. Regan has often shown deference and loyalty to the president, White House officials said.

Reagan, in turn, "has grown to trust and respect" Regan, Fuller said. Throughout his political career, Reagan often has surrounded himself with self-made, competitive industrialists like Regan.

"I'm one who believes in practicing what you preach," Regan said. "Now that may make me unique. It certainly made me unique on Wall Street -- 'Good heavens, he's a capitalist who wants to practice capitalism, which means competition.' They didn't like that. Still don't, that's why I'm not exactly a revered figure on Wall Street. But who am I? That's who I am. A guy that likes to compete, who will compete, but wants the rules to be even. I only believe in handicaps in golf . . . . "

Darman said of Regan: "In a business that is highly competitive, he has the instinct for success."

Regan also has shown a sense of humor. One day in 1982, the legislative strategy group was meeting on the big tax bill, debating the question of who would be affected by taxes on wine, as opposed to beer.

Some aides said wine was a rich man's drink and that the poor drank beer. But Regan insisted that poor people also drank wine, and after the meeting he sent the others a bottle of $3 wine with a note:

"Taste this and see what I mean."