After long weeks of debate, President Reagan, who really would have preferred to let his Council of Economic Advisers fade out of existence, was persuaded to keep it going with the appointment of Beryl W. Sprinkel as chairman.

The academic community, which has supplied all but a couple of members for the three-person CEA since its inception in 1946, heaved a sigh of relief: The chairmanship has been vacant since Martin S. Feldstein quit early last summer, unable to persuade the president that the expanding federal budget deficit was enough of a danger to the economy to warrant a tax increase.

It is important to maintain a high-quality economic council to provide solid economic guidance to the president -- whether or not he discards it for political or other reasons. As Erwin C. Hargrove and Samuel A. Morely of Vanderbilt University wrote in a study of the CEA after in-depth interviews with 10 former CEA chairmen:

"The president has a strong incentive to see good economic advice on the theory that knowledge is to be preferred to ignorance. . . . The president should know and want to know both the economic and political costs and benefits of alternative choices."

But after Feldstein left, neither of the two remaining CEA members -- William A. Niskanen Jr. and William Poole -- was designated chairman or acting chairman, and the president and his staff made it clear that the council would have no top advisory functions. Poole quit in January, and Niskanen, who completed the council's annual report to Congress, is about to depart as well.

President Reagan always has had a low opinion of economists. He was said to be "underwhelmed" by his first CEA chairman, Murray Weidenbaum, who joined up in the 1980 campaign after working initially to get the nomination for Big John Connally of Texas.

But Weidenbaum, a former assistant Treasury secretary in the Nixon administration and an expert on deregulation, came aboard after the original supply-side, monetarist scope of Reaganomics had been defined in 1981. And because Weidenbaum was neither a monetarist nor a supply-sider, he tried to bridge the gap between the two sides. It didn't work, and Weidenbaum quietly went back to St. Louis in less than two years.

Feldstein, a brilliant and orthodox conservative from Harvard University, took over from Weidenbaum. But the White House soon tired of his free-wheeling operation, and soured on him after he persisted in generating what the staff regarded as overly pessimistic forecasts. When he went public with his tax-increase demands, Chief of Staff James A. Baker III cut him down to size. He left last May, and many of his peers -- even those who agreed with him on the deficit/tax issue -- thought that Reagan was right in demanding an economic adviser who would not criticize his policies publicly.

For four years as undersecretary of the Treasury for monetary affairs, Sprinkel, a dyed-in-the-wool monetarist, rigidly followed one basic tenet: The most important variable in the whole economic system is the growth of the money supply; if the Federal Reserve maintains a slow, steady, growth of the money supply, that's all that is needed to assure a healthy, noninflationary economy; almost nothing else matters.

Sprinkel also irritated Europeans by insisting that deficits have nothing to do with interest rates, and that the dollar is not overvalued, merely high -- and mostly for reasons or failures for which the Europeans themselves are responsible.

He is a strong opponent of intervention by governments in foreign exchange markets. But he was overruled and silenced on that issue by former Treasury secretary Donald T. Regan.

Over the years, Sprinkel has been consistent in his economic ideology, and has spoken clearly and forcefully in defense of his beliefs. As a reporter who has known him for 20 years, going back to his days as economist for the Harris Bank of Chicago, I have never found him anything but candid and open. (However, he refused a request for an interview for this article because he has not yet been confirmed by the Senate.)

When Regan and Baker engineered their now-famous job switch at the beginning of the second Reagan term, Regan proposed solving the "CEA problem" by taking Sprinkel with him.

That worked in one way for Baker, who took Richard Darman of the White House staff to Treasury as the deputy secretary -- and Darman had an interest in the international economics field that fell under Sprinkel. But there was hesitation over inclusion of Sprinkel as a member of the Troika of top economic advisers -- the Treasury secretary, OMB director and CEA chairman.

However, the whole policy-making structure in the White House is likely to be reshuffled under Chief of Staff Regan. Domestic economic policy is likely to be shared equally by Regan in the White House and Baker at Treasury, with Baker the spokesman. Other key players will be Darman, and John A. Svahn, an assistant to the president whose earlier role has been upgraded by Regan. So long as he stays, OMB Director David A. Stockman also remains influential.

Now enters Sprinkel, as Regan's personal choice to take charge of a CEA that almost had expired. "I think this means that the CEA is on the road to recovery," someone close to the scene said on condition that his name not be used. "Don Regan will see that Sprinkel is involved, and Sprinkel will be the team player that Feldstein was not."

One thing working in Sprinkel's favor is that, as a monetarist, he doesn't worry too much about budget deficits: he wholly supports the present administration line that the way to deal with the deficit is to cut spending.

Last Nov. 1, in a pre-election debate with Democratic economist George Perry at American University here, Sprinkel said "the size of the deficit is a major problem, but tax increases are an unwise policy. That would only validate past overspending and pave the way for more."

As a good soldier, Sprinkel -- along with Regan -- went on the campaign trail for Reagan as a major spokesman on economic issues, and said all the right things: "This recovery is no fluke," he assured the audience at AU. "And it's due to Reagan's policy, which got the dead hand of government off the economy." And as for a tax increase, "That would be antigrowth, anti-opportunity."

A delicate question that remains to be resolved is how Sprinkel, as CEA chairman, will get along with Fed Chairman Paul Volcker. Weidenbaum and Feldstein, as well as their predecessor in the Carter administration, Charles Schultze, had a friendly, one-on-one informal relationship with Volcker, often getting together for a regular weekly lunch.

But Sprinkel was one of the administration's main "Fed-bashers," a harsh and public critic of Fed policy until he was silenced by Regan. Sprinkel likes to talk about the "right kind of monetary policy," and in his role as Treasury undersecretary, didn't hesitate to define it. Now, to maintain effective relationships with the Fed in his new role will require a different approach. Administration comments on Fed policy are likely to come from Baker, not CEA Chairman Sprinkel.

Finally, there is the question of what the relationship will be between the president himself and Sprinkel. It's not the Reagan style to have one-on-one relationships with Cabinet-level members. Feldstein, for example, never saw Reagan alone to discuss an economic problem. By contrast, Schultze had a weekly private session with President Carter. Historically, the most effective CEA chairmen have been those who were able to generate a close, trusting and personal relationship with the president.

The heyday of the CEA's influence may have been in 1962 and 1963 in the Kennedy administration under Walter W. Heller. Economists were highly regarded in those years, and Kennedy liked to consider himself an egghead who could deal on a first-hand basis with his brilliant CEA threesome of Heller, Yale professor James Tobin and the late Kermit Gordon.

Another peak time for the CEA was during Alan Greenspan's tenure under President Ford. Greenspan, a golf-playing confidante of Ford, may have been his top domestic adviser. Other highly influential CEA chairmen were Arthur M. Okun for President Johnson and Arthur F. Burns for President Eisenhower.

Burns had an especial role in CEA history: He came into the chairmanship in another period when the council was faced with extinction, in May 1953. A dissatisfied Congress had let funds for the CEA lapse, but was persuaded to change its mind when the distinguished Burns came aboard.

Sprinkel faces a similar task of rejuvenation, but with none of Burns' clout and with little personal relationship with Reagan to back him up. Sprinkel will be dependent on Regan. Some suspect that it will be Regan's, not Reagan's, economic council. But if Sprinkel can keep the institution going for the next four years, he will have performed a valuable service.