Why Chernenko?

After President Nixon's resignation, a well-informed Moscow lawyer asked the New York Times Moscow correspondent, Hedrick Smith, ''When will (the late Sen. Henry) Jackson become president?'' Assuming Watergate was a tactic employed by those opposed to Nixon's policy of detente, the Moscow lawyer had drawn the conclusion that now that Nixon had been forced from office his chief opponent would succeed him.

Such assumptions may strike Americans as incredibly uninformed, but our insight into the mechanisms that govern Soviet successions seems just as flawed. It is a measure of how little we know that, to the best of my knowledge, before Yuri Andropov's death no senior Sovietologist singled out Konstantin Chernenko as the most likely candidate to replace him. Even CIA reports placed Chernenko only fourth in the lineup of probable successors, after Politburo members Mikhail Gorbachev, Grigori Romanov, and Dmitri Ustinov.

Although the proper reaction to such a dismal forecasting record may be to throw up one's arms in despair, Chernenko's accession to power could possibly be an indication that Soviet successions may be more institutionalized than anyone imagines. In this respect, they may share some similarities with US successions, in which, if the president dies or is removed from office, the vice-president succeeds him, regardless of age, political orientation, stature, or qualifications.

There may be a semiformal mechanism in the Soviet Union whereby, if the general secretary dies or is removed from office, the second secretary replaces him. The historical evidence is consistent with such a supposition. Konstantin Chernenko was second secretary when Yuri Andropov died, and Chernenko succeeded him. Yuri Andropov was second secretary when Leonid Brezhnev died, and Andropov succeeded him. Similarly, Leonid Brezhnev was second secretary when Nikita Khrushchev was removed from office. The Soviet leaders may have evolved a system in which the No. 2 man in the Communist Party Secretariat is the agreed-upon heir apparent in the Kremlin.

Such an arrangement runs counter to the dominant image of Kremlin successions as involving power struggles unencumbered by formal rules. Certainly, if such a rule exists, the Soviets have never revealed it publicly. But it does seem to make a certain degree of sense to have some rules to ease the very delicate problem of succession. And, if one must devise a system, it also makes some sense to have the No. 2 man act as the successor to the No. 1 man.

The existence of such an arrangement could explain why it took several months for Kremlin leaders to decide on a successor to Mikhail Suslov when he died in early 1982. Suslov was second secretary at the time, and, as such, perhaps Brezhnev's designated successor. If, in choosing a second secretary, the Kremlin leaders were not just choosing a new ''chief ideologue,'' but also Brezhnev's successor, then clearly this was a weighty decision which would have taken some time. In addition, the two contenders for that post, Andropov and Chernenko, did become the next two leaders of the USSR.

In 1964, such an institutionalized procedure may also have determined the succession to Khrushchev. According to Zhores Medvedev's recent book ''Andropov, '' Brezhnev had been appointed to the post of first secretary (later changed to general secretary in 1966) ''as a compromise figure and because he had officially held the second position in the party since 1963.'' In Medvedev's version of the succession, Brezhnev was not the main actor in unseating Khrushchev. Suslov and KGB chief Alexander Shelepin were, instead. Nevertheless, as second secretary, Brezhnev became the new party leader and was later able to use the leverage of that position to consolidate his power.

This hypothetical arrangement could also explain why Chernenko succeeded Andropov despite his perceived liabilities as a has-been from the Brezhnev era. In fact, Chernenko may have received the second secretary's slot as a palliative when Andropov took over, with plans to replace him in due time. But Andropov's rapidly deteriorating health may have interfered with these plans, allowing Chernenko to retain his position and succeed Andropov. Similar things have occurred in US politics, in which vice-presidents have been chosen for temporary coalition-building reasons, then later succeeded to the presidency on the basis of their formal position.

Of course, the rules governing Kremlin successions may not be so simple. Even if they are, this would still not enable us to gauge who will be selected as the new second secretary and under what circumstances the occupants of this office may be replaced. Nevertheless, such a theory can be tested easily, while succession analyses that rest on factional politics cannot. It will be interesting to see if the pattern of the second secretary's accession to the top position occurs during the next transfer of power in the Kremlin.