Once again, this capital is in the agonizing throes of trying to whip together a budget for the new fiscal year -- this time in the wake of an election that sent a message to congressional Republicans and Democrats alike that the nation is getting restive with recession and unemployment.

Pretty obviously, the nation will have to spend more money on jobs and training programs. But how much can it spend to stimulate the economy when the budget for fiscal 1984 already appears to be something like $175 to $200 billion in the red? Can this problem be solved by squeezing the antirecession needs out of the bloated defense budget?

Or can the economy get a shot in the arm by advancing to Jan. 1 the 10 percent tax cut scheduled for mid-1983? President Reagan said the other day that he finds the idea "appealing." So does Treasury Secretary Donald T. Regan, but Economic Council Chairman Martin Feldstein isn't convinced.

Or, should the shot in the arm come from the Fed? Chairman Paul A. Volcker seems reluctant to be perceived as giving up his ritualistic anti-inflation posture, even though he has conceded publicly that the world faces the prospect of a critical deflation.

And, finally, when you get right down to it, is the whole business of budget deficits highly exaggerated? Don't our respected rivals, Japan and West Germany, run even bigger deficits than we do, as a percentage of their economic activity?

These are the questions being batted around in Washington today, in a tense and uncertain atmosphere. And my sense of it is that neither the White House nor the Democratic leadership is sure of which way to go. The Democrats would like to get some jobs programs going, and Speaker Thomas P. (Tip) O'Neill is still flirting with the idea of trying to get a dangerously protectionist bill, the "local content" requirement on domestic auto production, passed in the lame duck session.

Congressional Republicans, as House Minority Leader Robert Michel and others have made clear, have heard the voters talk. They do not plan to "stay the course" originally set out by Reagan -- concluding that, if they do, they won't be back in the next Congress.

The president, meanwhile, seems to have set his mind against any trims in the defense budget, or paring back the tax cut, hallmark of Reaganomics. He exudes confidence in an economic recovery that few others see, trumpeting the decline in interest rates and inflation as signs of the success of his program.

But Sen. Pete Domenici (R-N. M.), chairman of the Senate Budget Committee, echoes the consensus in and out of government: "Recovery in 1983 will be anemic, at least by historical, post-recession standards." He wants to put more stress on economic growth, less stress on the budget deficit.

But Feldstein worries about the deficit, which he feels keeps "real" interest rates high. As a matter of fact, Feldstein predicts that "real" rates -- nominal rates minus inflation -- will rise further.

This distinction between nominal or market interest rates on the one hand, and "real" interest rates on the other is never made by Reagan or White House politicians, but it is all-important.

As Feldstein pointed out the other day, record high "real" interest rates are what cause America's box-car sized trade deficit, generating protectionist pressures. In response to these rates, investment money pours in here, and the dollar soars in foreign exchange markets. That makes it harder for American exporters to sell goods abroad (because they are priced in dollars). Imports, priced in cheap yen, pounds or marks, come cascading in and gain a competitive edge with American products in third markets.

But, even more significant, high "real" rates discourage investment and the creation of new jobs in America. Lacy Hunt, vice president and economist for the Fidelity Bank in Philadelphia, has compiled a simple little chart that makes this point clear:

In 1981, when the prime rate averaged 18.87 percent, the consumer price index was 10.3 percent, and the "real" or deflated prime rate was therefore 8.57 percent -- a stunning increase from the 1.77 percent real rate of 1980. Then, the prime rate started to drop -- to an estimated 14.93 percent average for this year. But with the CPI for the year at an estimated 6.2 percent, the real prime rate is not lower, but higher: 8.73 percent.

Hunt's forecast is for a prime rate of 12.50 percent in 1983. But with a drop in the CPI to 4.5 percent, the real prime rate will still be a discouraging 8 percent.

When the tax factor is added in, the picture looks even worse: In the 1970s, when taxes were higher, corporations borrowing money could write off more of their interest cost. Thus, the real cost of borrowing money, after adjusting for both inflation and taxes, was actually negative for most of the 1970s. But now, with real prime rates higher, and the tax burden lower -- meaning less can be written off -- there is a high positive cost of borrowing money. It was 3.7 percent in 1981 and is estimated at 4.3 percent in 1982.

What everybody talks about, on the Hill and at 1600 Pennsylvania Ave., is getting the deficit down. But getting the deficit down by itself won't lower real interest rates.

For that to come about, Volcker will have to become convinced that he can safely push market interest rates down even further. Friday's discount rate decrease was a start. If it isn't followed up with others, the current world-wide recession could wind up a true world-wide depression.