Leonid Brezhnev, beset with deafness, flagging energy and other infirmities of age as he nears his 72nd birthday, demonstrated anew last week that his political clout and personal views on improving the troubled Soviet economy remain vigorous in his 15th year of power.

He reshuffled the Politburo in a way that strengthened his position and perhaps ensured that one of his longtime associates eventually will succeed him at the Kremlin pinnacle.

And in a long, tough speech, he confirmed his support of central planing, but acknowledged that innovation is needed to solve lagging economic performance and warned that a day of reckoning may be fast approaching for "those who fail" to curb the waste and inefficiency that is causing mounting leadership concern.

Little is known about how power is divided or policies are made in the Kremlin, whether Brezhnev rules by genuine consensus or presides because of unresolvable rivalries among the others, or a combination of these and other factors. Therefore, no Western analyst is comfortable confidently predicting what the changes of the past week could mean in a Kremlin without Brezhnev.

But what is clear is that with the installation of one longtime confidant, Konstantin Chernenko, in the front rank of the 13-member Politburo, and the accession of another, Nikolai Tikhonov, to nonvoting Politburo status, the grip of the Brezhnev inner circle tightened on the Kremlin. Underscoring this, the Politburo removed from leadership (ostensibly on health grounds) Kiril Mazurov, who shared with Premier Alexei Kosygin both responsibility for running the economy and an interest in attempting basic reforms more sweeping than envisioned by Brezhnev.

"Chernenko's Politburo elevation formalizes the fact of his personal standing with Brezhnev -- and also gives Brezhnev one more sure vote," commented one veteran Western Kremlin-watcher. He includes Brezhnev, Chernenko and Andrei Kirilenko, 72, second party secretary and a close associate for more than 30 years, within the so-caled "Dnieper mafia," now aging party bureaucrats who began their rise under Brezhnev's patronage 40 years age in the southeastern Ukrainian mining region.

Analysts who closely follow the speeches and travels of the Politburo believe that Kirilenko, a 16-year Politburo veteran with long administrative experience, is the most likely candidate to succeed Brezhnev as an interim leader. Despite his age (he is three months older than Brezhnev), Kirilenko appears energetic and often fills in for Brezhnev at party functions.

Both he and Chernenko have long dealt with administrative party matters. Chernenko's rise in a leadership whose members have an average of 10 years in the Politiburo, thrusts him to the forefront of any leadership prediction. He became a Central Committee member only seven years ago and a nonvoting Politburo member last year. He has traveled to Communist Party conferences in Greece and Denmark and was a member of the Soviet delegation at the Helsinki Conference on European Security in 1975.

Little else is known of him. He served Brezhnev beginning in 1950 as a propaganda expert, moved to national positions in the 1960s and in 1976 was named to the secretariat of the Central Committee, which has powerful authority in administering the Politburo policies. Only Brezhnev, Kirilenko and party ideologue Mikhail Suslov, 76, also occupy dual positions like Chernenko.

Although his name is Ukrainian, the Soviets say Chernenko is a Russian, presumably an important leadership requirement (although Stalin was a Georgian). Chernenko's official Tass biography does not say if he is married or has children.

Combinations of age, illness, unwanted regionalism or job isolation seem to limit the chances of other Politburo members to elbow out the "Dnieper Mafia."

Counseling extreme caution in predicting about the Kremlin, some analysts emphasize that economic affairs have caused more difficulties for Politburo members than almost any other factor. They point out that former Politburo member Dmitri Polyansky, now Soviet ambassador to Japan, was sacked in 1976 as agriculture chief after a disastrous 1975 harvest that cost the Soviets millions in overseas grain purchases.

Sick or well, Mazurov, 64, was responsible for industrial performance which Brezhnev sharply criticized. Advancement of Tikhonov, Kosygin's other deputy, to nonvoting Politburo status was done, one analyst said, "because Brezhnev wants to make sure the next five-year plan [1981-5] is drawn up right." It also puts a Brezhnev man in direct succession to Kosygin.

Another example cited by analysts as a murky Kremlin sign worthy of interpretation was the sparse turnout of party leaders at the July funeral of Politburo agricultural expert Fyodor Kulakov, who before his unexpected death at age 60 was accounted a possible Brezhnev successor. But when few Politburo members showed up at the funeral, analysts said they were signaling disagreement with Kulakov agricultural policies.

"They were telling the party men in the [provinces] to line up with Brezhnev," said one analyst.

It is thought now that Kulakov displeased Brezhnev on a variety of issues including favoring apartments for collective farmers as a cost-cutting move, but one that has resulted in fewer private plots being tended. Private plots are crucial to Soviet agriculture: more than a third of all market fruits and vegetables come from private ground, which accounts for little more than 1 percent of all cultivated land.

Following this line, the analysts say that instead of promoting Kulakov's deputy, Vladimir Karlov, to the top of Soviet agriculture, Brezhnev's leadership chose instead a regional party man, Mikhail Gorbachev, 47, of Stavropol region, and advanced him to the Central Committee Secretariat to watch over agriculture as a loyal Brezhnev choice, one without allegiance to the policies of the late Kulakov.

It is clear that Brezhnev and the leadership are deeply concerned by the troubled expansion of the economy, despite a record 235 millionton grain harvest and gross national product growth of about 4 percent this year. Steel, coal, energy and other major industrial indicators grew at rates lower than called for by the five-year plan.

Although more than $70 billion has been invested in new steel, oil, gas and coal production in the past three years, Brezhnev asserted, production lags because of sloppy work and "slack control over fulfillment of plans." Meanwhile, wasteful consumption practices continue, he said.

He pointed out that the volume of incomplete construction, which in 1975 stood above 60 percent of all projects begun that year, continues to climb.

"Uninstalled equipment worth several billion rubles lies uselessly in warehouses," he said. "Mention of this has been made more than once. There are no signs that Gosplan [the state planning commission], those who ordered this equipment, are conscious of immobilizing these investments, equipment and materials."

He criticized Gosplan for failing to accelerate production of consumer goods as called for by the party and said "some workers in the planning and management bodies" persist in cutting allocations for consumer goods, long a sore point with Brezhnev, who has set consumer improvements as a major goal of his tenure and then cut them back sharply in favor of heavy industry.

He warned that manpower shortages projected for the 1980s must be offset by increased production of labor-saving machinery but said an eight-year program of "accelerated production" of these items adopted in 1973 had produced nothing so far.

"How are we to explain the fact that despite our many obvious successes we have been consistently incapable of eliminating bottlenecks?" he asked. He accused the "central economic bodies, ministries and departments" of being slow in "putting the entire economy on an intensive development basis."

Productivity and quality lag because of failures in the ministries, Brezhnev said, and warned that the party will "raise in due time and with proper emphasis the question of the personal responsibility of those who fail to ensure implementation."

But Brezhnev suggested no sweeping new initiatives beyond exhorting the planners in the cumbersome centralized bureaucracy to do better. This was in keeping with his conservative economic views and is sure to find favor with the party bureaucrats who have for so long given him their support.