THE switch of roles for Treasury Secretary Donald Reagan and White House chief of staff James Baker was an inventive way for the Reagan administration to keep two top talents in the fold without sacrificing their counsel and energies for the domestic economic challenge ahead. James Baker has proved himself one of the ablest negotiators Washington has seen. He becomes, as Treasury chief, the President's new economic spokesman. He inherits responsibility for tax policy -- and can take a fresh look at the Regan tax-reform plan, which has already provoked great controversy. Mr. Baker has wanted a visible post in the Cabinet; he might have preferred secretary of state or attorney general. As a moderate who came to the Reagan entourage during Mr. Reagan's remarkable blending of George Bush and Reagan campaign managers in 1980, he has won the highest respect from all but those most aroused by the split between the moderate and conservative wings of the party. If Baker is ambitious to make a mark for himself in the Washington world, defeating the federal deficit will give him all the windmill he can handle for jousting.
Donald Regan had already reached the top of the investment management world before he went to Washington in 1981. Whether he will have the patience for the endless capital intrigue, the preparation of position and decision papers for the President throughout the second term, remains to be seen. He has certainly had experience in the Cabinet form of government that Mr. Reagan prefers. Mr. Regan will retain his Cabinet and National Security Council status. By replacing Baker as chief of staff, Regan eases conservative fears that the man closest to the President day by day might not share the President's fundamental views. Without Jim Baker in the White House, they won't be able to blame the President's aides for his decisions.
For all the leaks -- a good proportion of them deliberate -- about policy development and the evident consistency of the President's attitudes, the Reagan decision procession remains something of a mystery. It is warned, by some who worry about the emergence of a deputy presidency, that he can be misled. But all top aides who have tried to push or commit or argue the President in a direction he has not wanted to go have ``broken their picks,'' in Baker's phrase.
There is no room for anyone but team players in the Reagan administration. And ultimately one man, the President, makes the decisions. Mr. Reagan returns such loyalty by his own efforts to keep his team intact; he will often stick by a beleaguered aide far beyond what political expediency requires. How much of this inertia of loyalty is at work in the Baker-Regan switch can only be guessed.
The possibly more serious observation about Mr. Reagan's leadership style is that he can be passive about all but the most urgent programs, that he does not personally take on crusades the way a Lyndon Johnson would with civil rights, or Richard Nixon with his diplomatic initiatives, or Jimmy Carter his Camp David and energy projects. The compensating side of the Reagan style, of course, is the sense that the White House does not itself become a source of agitation in a world that is already troubled enough.
Still, the focus of White House efforts should be on resolving the big issues ahead. On the economy: deficits, spending, taxes, the defense buildup, trade policy. In foreign affairs: arms and summitry with the Soviet Union, the reassuring of allies, defining regional policies for troubled areas like the Middle East and Central America.
The internal administration debates on all these topics are as intense as ever. The President does well to keep able men like Jim Baker and Don Regan close at hand.