He is a lone Texan among a cadre of Californians, an outsider among insiders, a born-to-the-manner millionaire among middle-class advisers whose fortunes and adult identities have been linked to Ronald Reagan.

He is White House chief of staff James Addison Baker III, who after 18 months has emerged as undisputed first among equals in a collective leadership that also includes three Californians: deputy chief of staff Michael K. Deaver, White House counselor Edwin Meese III and national security affairs adviser William P. Clark.

Amid the shifting fortunes of the Reagan supporting cast, including the departure of a national security adviser and a secretary of state and the apparent diminishment of Meese, Baker has gained steadily in authority and reputation.

Though his formal authority falls short of the power accumulated by White House chiefs of staff in prior administrations, the 52-year-old Houston attorney is considered the most competent, articulate and best organized of Reagan's lieutenants.

He is respected on Capitol Hill, by the bureaucracy and by the White House press corps. And, alone among the top level of Reagan advisers, Baker is perceived to have an independent political future.

"Baker is a comer and a climber," said an administration insider who knows him well. "He is going to be a major force on the political scene for the next 10 or 15 years regardless of what happens to the president, almost regardless of what happens to the Republican Party. He has been in a position to develop some strong allies and some very strong and valuable ties . . . . I think that he is ambitious. I think that he wants to be president of the United States someday. I wouldn't bet it wouldn't happen."

Baker does not fuel such speculation. He goes out of his way to discourage it.

Entering the White House with the stamp of having managed Reagan opponents Gerald R. Ford and George Bush, Baker has made his mark by keeping his head down, forging a productive relationship with the president, mastering the White House organizational machinery and directing a legislative strategy that has produced some dazzling and unexpected victories.

Except on the far right, where Baker is darkly suspected of being the central manipulator in a cabal loyal to Bush, the chief of staff gets credit from many quarters.

Old Texas friend Robert S. Strauss, the Democratic outsider who tried to be an insider in the Carter administration, said he thinks Baker "is doing the chief of staff's job better than anyone has done it in any administration."

A Democratic congressional staffer said Baker is "a tough, practical politician" who holds the respect of the House Democratic leadership. Bush said Baker has "the confidence of the president" and of his peers. Deaver, the presidential assistant closest to Reagan, said Baker has the "refreshing habit" of never letting problems fester and of going directly to the source of any conflict.

"He's very well organized," Deaver said. "He has a good staff. He never puts anything off. And he enjoys making decisions. Now these are traits that make for a good executive, as far as I'm concerned. He forces decisions, and he makes decisions on his own . . . , and after the decision's made, there's no recriminations, he gets on to the next job that has to be done. He has a very good political sense."

Baker displayed this poltical sense on a recent trip to Oklahoma and Texas, where he faced two skeptical fund-raising audiences dominated by oilmen and the State Bar Association in Austin.

In Tulsa he skillfully preceded a litany of the campaign promises Reagan has kept with an anticipatory recital of three promises Reagan has not kept: ending draft registration, balancing the budget and reducing unemployment.

"No president can keep all of his promises," Baker said blandly, before launching into a peroration that concluded: "The bottom line, ladies and gentlemen, is that the president is sticking to his program."

And before the Texas bar Baker displayed that commitment to process that is the central feature of his political approach. After defending Reagan, Baker deplored the "denigration of the presidency," which he said he believes has undermined the ability of the United States to govern itself.

Expanding on this theme in a discussion with a reporter on the plane, Baker said, "We've got to find a way for our presidents to succeed--almost, if necessary, in spite of themselves. I would say the same thing about a Democratic president. The nation is successful when a chief executive is strong and successful. It's almost mutually exclusive to have a strong nation and a weak presidency."

Baker's political sensitivity and directness are appreciated on Capitol Hill. Senate Finance Committee Chairman Robert J. Dole (R-Kan.) recalled the time during the bipartisan budget negotiations earlier this year when he called Baker with what he believed could be a solution to the impasse.

"The answer was 'No,' but he called me back in five minutes," Dole said. "And you knew he had checked it with the president, not just read the paper in the meantime. He levels with you. He'll talk to you, he'll go out and speak for you. He commands a lot of respect."

Old friends and associates say the same. Marine Corps officers (Baker was one in the early 1950s) are supposed to have "command presence." Baker's peers rate him high on this count.

Republican Party official Nancy Thawley, who grew up three doors from Baker in a wealthy Houston neighborhood, remembers that when the children "played commandos he was always the general, and we had to be the Army. He did it very naturally. We always assumed he would be the general."

Even some of the hidden warts on the nearly unblemished public portrait appear to be extensions of virtues. He is so loyal to his personal appointments that, in the opinion of one of them, he is sometimes overly tolerant of sloppy performance even though at times he has been sharply critical of the overall inferior quality of the Meese staff.

Baker's natural reserve, which strikes some as bordering on aloofness, can be considered a strength or weakness or both. His judgment is good, but he tends to be so deliberate and careful that he is sometimes perceived as overly cautious or even timid.

One well-informed administration official said that President Reagan, during a conversation, expressed the view that Baker might even be "too timid" to run the White House.

The official said he sees this as a misperception. Like others who know Baker well, the official said he senses there the caution of an ambitious man.

In the White House, Baker's innate caution has been heightened by the realization that he has worked with Reagan for only two years, counting the 1980 general election campaign, while Deaver, Meese and Clark have known Reagan for more than 15 years. The caution is accentuated by Baker's hypersensitivity to criticism from conservatives who believe he has an agenda that is more moderate than Reagan's.

Richard Viguerie, publisher of the Conservative Digest, praises Baker as an organizer, and says he has become "virtually indispensable" to the White House. Baker's organizational skills are so superior to those of the Californians, Viguerie said, that his triumph as the preeminent White House aide was "no contest."

But Viguerie, an early supporter of John B. Connally, also sees Baker as a moderate "who believes in the precepts of Gerald Ford and the Fortune 500" rather than the more conservative course charted by Reagan. Viguerie cites the appointment of key moderates on the White House staff, notably presidential assistant Richard G. Darman and communications director David R. Gergen.

"It's not a Machiavellian or evil type of thing," Viguerie said. "Baker is very good. Put me in the same position with a moderate Republican president and I'd try to move him to the right."

Texas friends view Baker as more apolitical than moderate. His great-grandfather founded the law firm of Baker & Botts, now one of the 20 largest in the country, and his sons for two generations after ran the law firm and stayed out of politics. Baker's grandfather issued standard advice to young attorneys: "Work hard, study and keep out of politics."

Baker's father, James A. Baker Jr., probably provided the impetus for a less traditional Baker family career by deciding to send his son to Princeton for his undergraduate education. This was followed by service in the Marines and graduation with honors from the University of Texas Law School.

"What came out of this was a nice mix of Princeton and Texas, high society and cowboy," said one of Baker's associates. "He somehow manages to pull it off. On some Saturdays you'll see him with a chaw of tobacco, rough-out boots and that battered cowboy hat. On others he'll appear in a neatly tailored blue blazer, Northeast establishment slacks and tassel loafers. It's unusual that a person can bridge those two worlds so easily."

Baker drifted into politics when he was 40, partly because his first wife, who had died of cancer two years earlier, had been involved in the Texas campaigns of Bush. Baker wound up managing the unsuccessful Bush Senate campaign in 1970.

Five years later, with Bush's assistance, Baker was named undersecretary of commerce under Rogers C.B. Morton. A year later, with President Ford facing a stiff challenge from Reagan for the Republican presidential nomination, Morton brought Baker into the Ford committee as chief of delegate operations.

It was this post that catapulted Baker into national politics. At the time, Reagan campaign manager John P. Sears was saying that various uncommitted delegates would swing to Reagan. Baker, convinced that Ford had a majority of delegates, countered with candid delegate counts that revealed some short-term losses but created a credibility that paid off in the long run.

"I never had any significant contact with the press until I was thrown into the Ford campaign in May of 1976," Baker says today. "And in my view I was successful, certainly in the delegate process, and in the campaign itself individually because I was candid and forthright with the press. More than any other single thing, that's what gave me whatever reputation I have--it framed my view of press relations."

It is an approach that some would say has not fully survived the resignation of Secretary of State Alexander M. Haig. Jr. On Baker's recent Texas trip he was asked during a brief Austin news conference whether he was glad that Haig had resigned, and began his answer, "No, I'm not," a statement that defies all known descriptions of Baker's feelings on the subject.

One of the anomalies of Baker's career in electoral politics is that he has lost rather consistently but is widely regarded as a winner. He lost with Bush in 1970, with Ford in the fall campaign in 1976, with himself as a long-shot candidate to become the first Republican attorney general of Texas in 1978 and with Bush again in the 1980 presidential campaign.

But before Bush had even conceded, Deaver and flamboyant Reagan campaign adviser Stu Spencer were recruiting Baker on the Reagan team.

In the fall campaign Baker became the chief debate negotiator, and succeeded in persuading President Carter's advisers to engage in what proved to be a ruinous face-to-face meeting with Reagan. At Deaver's suggestion, and with the support of Spencer and Nancy Reagan, the president-elect subsequently chose outsider Baker over insider Meese as his chief of staff.

From the first day, Baker showed that he knew what to do with the authority that had been given him. While the Washington streets were still littered with the debris of the inaugural parade, Baker stood with Meese in the counselor's office and flatly refused, in the president's name, to approve a proposed executive order presented him by Haig that would have given the secretary of state control over a number of inter-agency groups. Neither man ever forgot the encounter, and the executive order was never approved.

Before the month was out Baker had given new meaning to the aphorism that whoever controls the staff controls the White House. Under an agreement hammered out with Meese the day after election, Baker controlled most of the White House staff. He proceeded to fill the key positions with hard-driving loyalists.

Operating principally through the caustic and hard-working Darman, a former Commerce Department colleague who has been called the "senior member of the Baker law firm," and working closely with Office of Management and Budget Director David A. Stockman, Baker became the chief architect of the Reagan legislative program.

The legislative strategy group, orchestrated by Darman, met frequently in Baker's office, and played a key role in the passage of the 1981 budget and tax bills and the Reagan victory in the vote on the sale of Airborne Warning and Control Systems (AWACS) equipment to Saudi Arabia.

Other vital staff appointments were also Baker people. These included Gergen, a controversial figure with the press but an idea man for Baker, plus legislative liaison Kenneth Duberstein, intergovernmental relations specialist Rich Williamson and executive assistant Margaret Tutwiler, who speaks directly and candidly to Baker and on his behalf to reporters, politicians and other members of the White House staff.

Gradually, Baker's superior organizational ability and the weight of his staff took the play from Meese. Even Meese's supporters were at times critical of his disorganization and in particular of his staff appointments.

One notorious example in the White House is how the proposal for a nuclear non-proliferation treaty stayed on the desk of a Meese assistant for 16 weeks after it had been approved by the National Security Council.

In January the shared leadership of the White House took on a new dimension when Clark replaced Richard V. Allen as national security affairs adviser and foreign policy was effectively removed from Meese's sphere.

Baker and Clark, one aide said, approached each other with wary respect as "two individuals who have excellent power antennae each recognizing that the other has the same power."

Meese, though diminished, did not fade away, nor is he likely to do so. Never the "deputy president" he was made out to be, Meese remains valued by Reagan as a synthesizer and summarizer. The counselor is now resisting what Meese's supporters describe as "a push" against him from the Baker camp.

Longtime Reagan watchers know that Reagan, who was burned by strongman leadership during an early scandal in his governorship and again by Sears' effort to force Californians out of the 1980 campaign, desires a collective leadership. They remember that Reagan fired Sears when the choice was whether to keep his campaign manager or get rid of Meese.

"With Reagan, it is a very precarious game to ask who is on top of the power heap, because ultimately he will decide it," one insider said. "There's a lot of things that the president delegates, but when it comes to people around him and when it comes to deferring to one person or another, when it comes to giving position, prestige or leverage, the president has some very specific ideas . . . . Reagan sees both Meese and Baker as valuable to him personally. I think that Meese and Deaver and Baker all know that none of them could go to the president and carve out an independent, more powerful role, because the president doesn't look at their functions in those terms at all."

Where this leaves Baker is a question. He has given out widely varying signals to administration officials and to those who care about him personally. He has confided on some occasions that he would "like to run his own shop" after the election, which many interpret as desire for a Cabinet post, preferably Justice.

He has said that he will do whatever the president wants him to do. Some who know him say they believe he is willing to stay on as chief of staff but would like his position strengthened.

Many say Baker has a long-range, structured game plan that will lead him into foreign policy, the most significant gap in his experience. One official even suggested that Baker might do what Bush had done and become U.N. ambassador if Jeane J. Kirkpatrick ever decides to leave that post. One widely shared view in the administration is that the president will have several Cabinet vacancies to fill after the November elections.

"I think Baker can do whatever he wants," said Deaver, who has been Baker's bridge to the Californians and to the president. "I think the president would like to have him right here for the entire four or eight years, whatever it is. I think that would be hard for Jim, or for anybody. Because that job takes too much out of you, you burn out after awhile."

Another staffer said Baker already is showing signs of this burn-out by an indifference to some of the problems facing the administration. If this attitude exists, it is uncharacteristic of Baker.

But those who know Baker best say they doubt that he would remain in a job in which he could not give his best.

"He has a sense of where he's going, that much I know," one of Baker's most devoted supporters said. "He wants to do a good job for Ronald Reagan, and he will. He also wants to do a good job for Jim Baker."