Dame Fortune is working for the Reagan administration in its fight against inflation. But the underlying surge of the economy is so powerful that luck isn't good enough.

So the administration, in a desperate move to squeeze the economy further, abandoned past positions on taxes and Social Security. It thereby fingered the missing piece in economic policy -- a program to restrain prices and wages.

Like most pleasant surprises, the luck in the fight against inflation comes in threes. First, a mini-glut of oil has led to a drop in the price of a commodity that has previously worked to force up inflation. Food prices, another past source of inflationary pressures, have also moderated. Third, the dollar has lately appreciated against other currencies, thus cutting the cost of imported goods.

A marked easing off in the Consumer Price Index has been the most visible consequence. The CPI registered a rise of 12.6 percent in 1980. The April numbers show the CPI rising at an annual rate of only 4.8 percent.

But a crucial difference separates external causes of inflation -- such as rises in commodity prices -- from the underlying demand pull of the economy. Many signs suggest that, while the external thrusts have abated, the inner drive of the economy, the demand for goods and services and capital and labor, continues high.

A veritable explosion in the growth of the gross national product -- up at a rate of 8.4 percent according to revised figures for the first quarter of this year -- flashes one sign. Figures on hourly earnings -- up at a rate of more than 10 percent during the last six months -- also express the strength of demand. Then there are the record interest rates.

Leading banks have recently raised the rate at which they lend to their best customers to more than 20 percent. That means businessmen and consumers are prepared to pay enormous premiums for credit. Why?

Part of the reason is that demand for goods and services is brisk enough to justify the high rates. Another element is that borrowers believe that inflation, instead of falling, will go right on rising. That expectation is fed by professional analysis, which finds that the efforts of the Reagan administration to put a lid on federal spending have not been effective.

The administration, in these conditions, felt obliged to build confidence in its anti-inflationary effort by acting to make still further cuts in both the federal budget and consumer spending. In that spirit, it aired proposals to curtail some Social Security payments. It also announced a willingness to compromise with the Democrats on tax legislation now before the Congress.

The Democrats found in the proposed Social Security cuts a splendid occasion for demagroguery. In the Senate they put forward a resolution condemning the president for robbing the aged. The Republicians saved the day only by a counter-resolution against cuts in Social Security payments.

Tax compromise seems promising. In the past, the administration backed a Kemp-Roth proposal for a 30 percent cut in personal income taxes to be applied over a three-year period. The Democrats favor a much lower cut good only for a year. Since Kemp-Roth would be wildly inflationary, the Democrats are in a position to bargain hard. They are doing the administration a favor by taking it off the Kemp-Roth book. So there are good prospects for tax compromise that will curtail the deficit by carrying only limited cuts, while holding down consumer spending by being particularly niggardly in reduction of personal income taxes. s

Still, the economy can hardly be said to be out of danger. On the contrary, a basic defect in the administration's economic plan has been exposed by the latest developments. Even with good breaks, the administration has to squeeze very hard on interest rates and federal spending to hold back inflation. Experience -- in 1966-67, in 1969-71, in 1974-75 and in 1979-80 -- suggests that tight money and tight budgets precipitate sharp recession before they really put a bite on inflation. With several companies -- including Chrysler and some of the thrift institutions -- in grave trouble, a tough anti-inflationary policy could stimulate something approaching panic in the weaker sections of the economy.

For true safety, something else has to be added to the squeeze on interest and budgets. The something else is a mandatory program for restraining prices and wages. With such a program, commodity gluts and softness in the economy would be translated into cuts in prices and wages. Once those started to fall, inflation would be truly unwinding, not merely in suspense. The economy would at last come off the knife edge where, for the past decade, it has been so perilously positioned.