He came into the Politburo on the coattails of Leonid Brezhnev, was passed over in favor of Yuri Andropov, and now finds himself at the top of the Soviet Communist Party hierarchy.
Washington wonders: Does Konstantin U. Chernenko's elevation simply represent the old guard on the Politburo hanging on to power and, therefore, point to ''business as usual'' in the Kremlin? Or is there some hidden spark in Mr. Chernenko that could ignite in unexpected ways?
Diplomatic and academic analysts seem to agree that the 72-year-old career bureaucrat was selected as a transitional leader who would operate in the collegial style. The oldest Politburo members are not prepared to relinquish rule and, in effect, chose whom they regarded as the least dangerous while giving the relatively younger members time to become carbon copies of themselves.
''The old boys are sticking together,'' comments an American official, ''and the leadership now will probably be more collective.''
At this early stage, the message from the Kremlin is continuity, say Reagan administration analysts. Chernenko's inaugural speech yesterday was virually a duplicate of the Andropov line, emphasizing the integration of Eastern Europe, support for liberation movements, and commitment to peaceful coexistence while maintaining the Soviet Union's military might. Echoing his predecessor, the new Soviet leader also placed major emphasis on getting the Soviet economy moving.
The conventional image of Chernenko is that of a lackluster party bureaucrat and paper shuffler who did not have the political skill to challenge Andropov's bid for power. Thereafter he played by the rules and stayed in the shadow. But some experts note that initial impressions can turn out to be wrong.
Dimitri Simes, a senior associate at the Carnegie Endownment for International Peace, says Leonid Brezhnev in 1964 also was chosen as a transitional leader against the background of a struggle between Politburo members Alexander Shelepin and Nikolai Podgorny. Yet Brezhnev ultimately emerged as ''first among equals'' and put his own stamp on Soviet domestic and foreign policies. Nikita Khrushchev also defied all previous assessments of his capabilities.
''You have to take into account that it was beneficial for Chernenko to act as he did,'' Dr. Simes says. ''Now you have a new ball game. He could demonstrate new qualities.''
Brezhnev had been head of state, however, and a key figure on the Politburo, other experts note. Chernenko came up through the ranks solely as Brezhnev's protege. Moreover, both Brezhnev and Khrushchev were much younger than Chernenko when they assumed the party leadership.
While predictions are risky, experts say, several aspects of Chernenko's record could have implications for the Kremlin's future course:
* He was closely identified with the Brezhnev policy of detente with the West.
* He consistently has favored decentralization of the economy, arguing that the party apparatus should not substitute itself for ecnomomic management, although the party should remain dominant.
* As party ideologist, he endorsed Andropov's crackdown on cultural freedom and warned against ideologically harmful foreign influences. But, contrary to the attitudes of many party officials, he preached that the party leadership should be attentive to feedback from the grass roots and backed sociological studies to probe public attitudes.
One of the hallmarks of the brief Andropov period was the campaign to energize Soviet society by a campaign for labor discipline. Chernenko was known to be less enthusiastic about that campaign because it began to reach into party ranks. But, now that the more demonstrative aspects of the drive have faded, he is expected to continue the effort to jack up labor discipline and weed out corruption, analysts say. Older men in the ministries have been retired, and changes are taking place in the party at the regional level.
In terms of invigorating the economy, the question is whether Chernenko has the energy and character to act on his beliefs. Reform of the Soviet economic system has always run up against political resistance because the men at the center to do not want to risk losing control. It would take leadership of uncommon imagination and daring to introduce sweeping changes. On the face of it , Chernenko does not fit such a mold.
''A weakness of Chernenko all along has been that he has never run anything, '' says an administration official. ''He has been a permanent staffer without much administrative experience.''
In any case, the view of most specialists here is that the new party secretary will have to move in concert with his colleagues.
''Obviously the Politburo is a consensus body and no one gets out in front,'' says a US official. ''The choice of Chernenko can hardly be seen as a bold move. It suggests a cautious status quo.''