If Leonid Brezhnev had publicly named a successor before he died, many Western observers of life behind Kremlin walls believe that man would have been Konstantin Ustinovich Chernenko, member of the Politburo, member of the Central Committee, and, most important, political confidant and personal friend of the Soviet leader for more than a quarter of a century.

It is Chernenko who has been pictured as the keeper of the gate for the Soviet leader in the final years of his life, a position all the more influential as Brezhnev's illnesses kept him from focusing for more than a few hours a day on the business of running the Soviet Union and its ruling Communist Party.

And it is Chernenko, a close working colleague, who was pictured as the man to whom Brezhnev turned when the levers of Kremlin power needed a pull.

Chernenko, 71, is a classic case of a man who rose to the top echelons of power within a closed political system by attaching himself to the right star.

His relationship with Brezhnev began in the 1950s when he served as Brezhnev's propaganda chief in Moldavia and followed his patron up to the national leadership. When Brezhnev became a national party secretary for Nikita Khrushchev in 1956, Chernenko became a national domestic propaganda chief.

Chernenko, born into a Russian peasant family on Sept. 24, 1911, eventually reached the Central Committee and the Politburo and was named one of the party's national secretaries. Few within the Kremlin hierarchy hold all three positions.

Most important for his relationship to Brezhnev, he served as head of the party's general department since 1965, giving him intimate knowledge of its inner workings and its leading figures both in Moscow and around the country.

For a period in the late 1970s, Chernenko was the youngest man in the Kremlin to function both as a full Politburo member and as a member of the powerful executive body, the Secretariat.

For all his influence and experience in the inner workings of the Kremlin power elite, his real standing with Brezhnev and his potential as a successor surfaced in an international setting -- the Brezhnev-Carter summit meeting in Vienna in 1979. There, it was to Chernenko that Brezhnev turned when he needed assistance.

Because of this exposure, Chernenko has been tabbed a relative dove in East-West relations, but observers caution that he appears to have little firm grounding in international affairs and his views on such subjects very likely would be formed in conjunction with those who supported him as leader.

It was after the death of long-time ideologist Mikhail Suslov, the party's number two man, that Brezhnev appears to have made a big push to consolidate Chernenko's position as potential successor, reportedly making sure his friend received ample television exposure and also assigning him at least some of Suslov's duties as ideological arbiter, according to some reports.

Little is known about Chernenko's personal life, his family or his leadership qualities, other than some indications that he is by no means a dynamic figure.

It remains to be seen whether Brezhnev's imprimatur carries as much weight in death as in life.