As Congress struggles with a new budget that will force it to raise taxes and take a further whack at welfare programs in an election year, despite grim economic conditions, Washington's rumor mills grind out a familiar but unconvincing theme: The president is unhappy with the economic advisers who have brought the nation to this sorry state, and he's looking for a new (and, of course, better) team to replace them.

It's an old form of scapegoating, and every administration indulges in it: When things go wrong, as they have with Reaganomics, the tendency is to shoot the bearer of the bad tidings instead of changing the policies themselves.

As is well known, the Reagan administration has been taking pot shots at Federal Reserve Board Chairman Paul A. Volcker for pursuing a tight-money policy that--the White House says--has driven up interest rates and caused the current recession.

Of course, the real problem is that the Fed's tight-money policy collides with the Reagan administration's easy fiscal policy, and it's this incompatibility that better explains the economy's malaise.

In any event, Volcker's term as chairman of the Fed is not up until August 1983. So any fancy footwork on the personnel side to detract attention from policy failures will have to come somewhere else.

One rumored scenario making the rounds goes this way: The president will dump Economic Council Chairman Murray Weidenbaum and Office of Management and Budget Director David A. Stockman, downgrade the responsibilities of both successors, and look for a new "czar" to run economic policy as efficiently as George Shultz did for President Nixon.

One of the secrets of Shultz's success in that role was that he was also secretary of the Treasury, and thus had the back-stopping of a (then) capable Treasury staff. But there is no indication (yet) that the president wants Treasury Secretary Donald T. Regan to step aside. If anything, Regan, who is a very good salesman, has maintained a close rapport with Reagan and the White House staff.

Well, who is it who might come into this new position of economic czar in the White House? Those who pass the rumors around offer the name of Alan Greenspan, an establishment-type Republican, former chairman of the Council of Economic Advisers under President Ford--a man highly respected in the business community.

The story has it that Greenspan had quietly discussed the scope of the new job with White House aides, even though they know he might better be tempted, at this stage of his career, by the Treasury job. Is there any fire underneath all this smoke? After all, some of it has been published by political pundits and at least one major news magazine. What better sources could you have? But Greenspan, who resisted great pressure to take a job at the beginning of the Reagan administration, claims it's all smoke.

That doesn't mean that there won't be a major reshuffle in Reagan's economic team next year, whether or not Greenspan is involved. Although he's done as good a job for Reagan in the present budget crisis as anybody could have, Stockman not surprisingly has never fully recovered from the self-inflicted wound of "The Education of David Stockman" in the Atlantic Monthly last year.

But Stockman, as enthusiastic as ever, would be hard to replace. "He's like the Mafia's bookkeeper," says a close friend, "the only guy in the administration who knows where everything is--all the deals and negotiations. If they got rid of Stockman, the guy who came in and sat at his desk would have one hell of a time reproducing what's been going on around there."

Not so with Weidenbaum, who was appointed in 1981 after the basic Reagan program was set. (In a way, that gives him a ready excuse for the history books.) He was effective early on in simmering down the supply-siders' outrageous forecasts. But playing the macro-economic game is not Weidenbaum's strong suit. Weidenbaum is under pressure now, from impatient political advisers around the president, who privately concede that current conditions are terrible. They were never terribly excited about Weidenbaum in the first place.

Some Washington observers expect that Shultz, as secretary of State, will get into domestic economic as well as foreign policy issues. Shultz certainly is better equipped to do that than was Alexander Haig--and the international economics problems will be better managed than heretofore. But he won't have the time or the staff expertise to play the total economic role he did in the Nixon administration.

So what does this particular rumor about a new economic czar add up to? A wise old hand confesses: "I've finally learned that, in Washington, there can be real smoke even where there is no fire."