In the 12 weeks since Mikhail Gorbachev became Soviet leader, he has been projecting an almost breathtaking determination to make changes in the Soviet economy. He has focused on this issue in a way suggesting that his political fate is interlocked with the fate of this program.

The 54-year-old Gorbachev's performance so far has beensmooth. The ease with which he consolidated his authority and the speed with which he assembled a new Kremlin management team have raised expectations that he may succeed where others have failed. Foreign observers see this as a possible trap, since expectations are running high while the leadership is not yet seen to have come up with a well-developed package of economic reforms.

The principal risk that Gorbachev runs is raising expectations for change that could be resisted and eventually thwarted by those bureaucrats who have vested interests in the current arrangements. Such a failure to deliver would damage his credibility in a populace that watches its leaders closely for any sign of weakness.

Most Soviets seem willing to give the new team more time to work out its program, which should be completed before the next Communist Party congress, in February 1986.

The ground for this smooth transition was prepared by Gorbachev's political mentor, the late Yuri Andropov, who not only selected the men who run the Soviet Union today but also laid down a strategic course for the rest of this century.

But this is only a part of the current picture. In a relatively short time, Gorbachev has managed to establish himself as a man of formidable political skills, an excellent public speaker, and a determined leader. That he has pushed Andropov's program with more vigor and persistence than did his immediate predecessor, Konstantin Chernenko, has been the source of considerable satisfaction for those elements in Soviet society that are advocating major changes.

Whether Gorbachev can restructure the Kremlin leadership should be clearer after completion of the current rejuvenation of regional and local Communist Party organizations.

Meanwhile, for the first time since Nikita Khrushchev, the Soviets have a leader who talks directly to them, who goes into the streets and factories, shops and homes, calling on them to join him to "get the country moving forward again."

Gorbachev is the first Soviet leader who is a genuine television personality and who adroitly uses the medium to his advantage. He is the first to push his wife, Raisa, into the limelight of publicity as a trusted aide who could help him mobilize Soviet women, who make up more than 50 percent of the population.

With the exception of old Bolsheviks during Lenin's time, Gorbachev is the first Soviet leader who can deliver an eloquent and stirring 1 1/2-hour speech without a text.

One night recently, many Soviet citizens intently watched television sets as he addressed the Communist Party organization of Leningrad. Several days later people were still discussing the speech as if it were a spectacular artistic show.

All this could reflect a mere change in style, rhetoric and personality, with the problems of a centralized economy run by a huge, immobile and hierarchical bureaucracy remaining intractable.

Two earlier attempts to modernize this edifice that is the world's second-largest economy have failed, and the question remains whether the system is susceptible to changes.

When one speaks about the Soviet economy, one speaks in effect about the whole society. Virtually all Soviet citizens work for the state. For more than 65 years, this economy has been run from the center by people who held certain utopian assumptions and tended to disregard the laws of economics.

What Gorbachev and his colleagues plan to do is "restructure" the economy, especially the machine-tool industries; modernize the existing capacities, introduce economic incentives to increase labor productivity, and set a steady rhythm for the economy.

But, as he said on television, not only the economy has to be restructured. "We are facing a major restructuring of our attitude, too," he said. Speaking about Communist Party officials, he warned that "everybody must change, from the worker to the minister to the secretary of the Central Committee," to increase labor productivity.

"Those who do not intend to will have to be moved from the road," he added.

What the planned "restructuring" of the economy is going to involve has not been spelled out.

So far, the specific measures included some tough antialcoholism decrees -- particularly to combat the current widespread drunkenness at work -- and a decision to distribute private plots of land to at least 1 million people each year. The latter decision seems designed to ease the country's food shortages.

Although Gorbachev has been talking tough, his public standing is very high, as it often is for leaders when things seem to be going right. How long this is going to continue is anyone's guess. But Gorbachev enjoys certain advantages suggesting that he may be in a position to make a major impact on the country.

First of all, he is relatively young. Secondly, he is the most visible of a whole group of relatively young men who have been rocketed to power and now form the Kremlin's management team.

All these men were handpicked by Andropov and they seem to share energy, apparent lack of corruption and a strong sense of purpose. Nobody would have identified them as future leaders before Andropov brought them from obscurity after he came to power in November 1982.

Yegor Ligachev, 64, now regarded as the second man in the party hierarchy, was a provincial party chief in Toms; Nikolai Ryzhkov, 55, was a relatively obscure economist; Vitaly Vorotnikov, 59, was in diplomatic exile in Cuba; Viktor Chebrikov, 61, was a largely unknown deputy to Andropov when he headed the secret police, and Gaidar Aliyev, 62, was the leader of Azerbaijan.

In addition to having a new team at the top, Gorbachev also has an opportunity to change the entire top echelon of the party at the congress in February. The congress will elect a new Central Committee, the party's top policy-making body, and there is little doubt that its new members are going to reflect the views of the new leader.