Six months into his presidency, Ronald Reagan has evolved a political style that fits his philosophy. It is simple: Less is more. Reagan is running an aloof presidency. He is not isolated or inaccessible -- a traditional complaint -- but he deliberately distances himself from all but the few issues, mainly the economy and reduced government, that are his main themes.

To a large extent, Reagan has had the White House on his own terms. Never was his political mastery more apparent than in his stunning House victory on the tax bill. It simply re-emphasized the basic political reality of 1980: Reagan is setting the issues; Reagan is creating the climate. The Democrats are reacting.

But to keep political control, Reagan now needs an obliging economy. The White House assumes that for most people the state of the economy matters more than any specific government program. The gamble is that the economy will perform well enough to justify less as best.

Otherwise, the president's considerable political strengths, may turn out to be illusory. Even his reputation as a superb "communicator" (a plain word like "speaker" apparently having gone out of style) rests on less is more. Reagan remains the master of the set political speech, but he has had only three press conferences. And in these, his command of both language and substance has lacked authority.

Reagan's narrow presidency may reflect his temperament and interests, but it rests fundamentally on a shrewd understanding of political power. More than anyone else, the president sets the national agenda. Unlike Jimmy Carter, who pronounced himself on every subject under the sun and some that weren't, Reagan projects his vision of limited government simply by ignoring much of what government does.

The most explicit acknowledgement of this comes from David R. Gergen, the president's assistant for communications. In a recent interview, Gergen said: "My concept is that the power of the presidency becomes a wasting asset if he comments upon every issue in the passing scene. It is better for him to speak out on the really important issues and let his lieutenants speak on a daily basis."

The White House's gamble that the economy will permit this sort of approach is less wild-eyed than it appears. Although the administration has taken a lot of guff for excessively optimistic economic projections, its own outlook does not differ radically -- at least in the next year -- from those of most private forecasters.

In the White House view, the economy will stagnate for the rest of the year, with unemployment rising to a peak of 7.7 percent in the fourth quarter. Then, however, a rapid recovery in 1982 will reduce unemployment to about 7 percent at the end of the year, while inflation (as measured by the deflator of the gross national product) also will drop to about 7 percent.

Compare that with the inflation and unemployment estimates of four major forecasters. Most see recovery in 1982 sufficient to bring joblessness below current levels (7.3 percent in June). At the same time, inflation continues to slide. All the figures are for the fourth quarter of 1982; the inflation figure is an annual rate of change.

Chase Econometrics Inc., inflation 8.2 percent, unemployment 6.9 percent; Wharton Econometrics, 9.4 percent, 7 1/2 percent; A. Garry Shilling, 7.0 percent, 7.0 percent; and Security Pacific Bank, 8.4 percent, 6 1/2 percent.

That so many forecasters have the same general outlook, of course, doesn't say very much, except that economists run in packs. The optimism could be misplaced. Inflationary pressures (especially wages, which show few signs of abating) could prove more stubborn than expected; growth could be less, unemployment more. But even the most pessimistic forecast -- Wharton's -- doesn't show much deterioration from today.

Should the economy do much worse, the strength and appeal of Reagan's style could fade. More than any other political figure since President Kennedy -- and perhpas exceeding even Kennedy -- Reagan excels as a formal orator. He reaches to his listeners' emotional gut, drawing out dormant feelings.

But Reagan's moral authority and credibility require an echo from the real world. He concedes this. Here he is speaking to the annual convention of the NAACP:

"Can the black teenager who faces a staggering enemployment rate feel that government policies are a success? Can the black wage earner who sees more and more of his take-home pay shrinking because of government taxes feel satisfied?. . . We will not concede the moral high ground to those who show more concern for federal programs than they do for what really determines the income and financial health of blacks -- the nation's economy."

Reagan's respect for words, his sense of timing and cadence gives his speeches polish. They conform with his generally affable and hopeful personality, adding an authenticity they otherwise might lack. But what seems powerful and heartfelt now can quickly turn sour and slick in the absence of corroborating evidence. In June the black unemployment rate was 14.2 percent, more than twice the white rate of 6.4 percent.

If the economy responds as the president hopes, his success will allow him to stay above many of the grimy, contentious issues facing his administration. If not, his political power base may erode and confront him with a double problem: taking more responsibility for the controversial activities of subordinates, and addressing the divisive social issues -- abortion, family planning, school prayer -- urged on him by conservatives.

The skimpy evidence so far suggests that the president is less adept at juggling intricate political problems than at projecting general themes. Even at press conferences, his frequent response to detailed questions is to veer off into meaningless generalities or to answer, "I don't know."

There have not been many sick jokes in the past six months about Ronald Reagan's acting ability. The truth is that much of his success reflects his impressive performance as a political actor. That is a Reagan strength, but also a weakness. For in the end, the audience demands more than a performance.