The recent pictures showing Leonid Brezhnev being propped up by his companions as he struggled to get out of an armchair during his visit to Bonn tell us a good deal about the relationship between him and his possible successors in the Kremlin. They are propping him up politically, too, because they need him as a symbol of stability while they maneuver for the seccession.

Brezhnev's main prop is Andref Kirilenko, the party secretary in charge of organization and the party's policy, who is following exactly the same road to power than was taken by Stalin, Khrushchev and Brezhnev himself. In one sense, he has already won the struggle. The road to power in the Soviet Union has always led through the control of the party organization, and that has been Kirilenko's major preoccupation for the past dozen years or so. He started exercising that control for Khrushchev in a small way, and has now ended up doing it in a big way for Brezhnev, whose poor health leaves little scope for the elaborate intrigues a Soviet leader must engage in if he is to keep his associates on their toes - and to prevent them from making a grab for his job. Khrushchev entrusted this work to Brezhnev - and that proved to be his undoing, for Brezhnev then used the power he had acquired to force Khrushchev's resignation "on grounds of health." But Kirilenko has no need to do the same to Brezhnev, whose health is so poor that he cannot supervise the bureaucracy effectively.

Since Kirilenko is older than Brezhev, he knows that his best chance of succeeding him lies in using the power he has accumulated to fortify his position at the top of the Kremlin hierarchy. If he is to accomplish that beyond the risk of a challenge, he needs even more time than he has had so far. President Nikolai Podgorny's challenge to Brezhnev last year showed that some of the most skilled Kremlin infighters believe that the Kirilenko-Brezhnev combination is not invulnerable. Hence it is in Kirilenko's interest to build up his own power while keeping Brezhnev where he is, as something of a figurehead, even at the cost of exposing him to the kind of embarrassment Brezhnev suffered in Bonn. A similar situation arose during the visit to Paris more than a year ago when those who saw the Soviet leader close up gained a clear impression of his debility

Brezhnev's periods of weakness are temporary, and they do alternate with periods of physical vigor. Some Western analysts note that he is alert and energetic at his best, and from that they conclude that he is still the boss. But they cannot know whether the things he says to Western officials when he seems in good form are his own views or things that have been dictated to him by the other Politiburo members. When Brezhnev, in his off-moments during his talks with foreign officials, manages to do little more than read aloud the paper prepared for him, it tells us something of what must also happen during the Politburo meetings when any policy dusputes that cannot be resolved at lower levels come up for settlement by the top leaders. When Brezhnev is not well, which is frequently the case, he must either absent himself from the meeting or read his prepared statement - and in either case his associates must know that the policy decisions to which he puts his name are really made by Kirilenko.

Why, then, do they not take advantage of this to push Brezhnev out to acquire the top post for themselves? The answer is that some of them have tried to open up the struggle for the succession, but, as the dismissal and disgrace of Podgorny showed last year. Kirilenko's control of the levers of power proved to be too strong. It also proved to be a warning for the others not to start anything they might not be able to finish.

The other potential challengers, the younger members of the Politburo who might aspire to Brezhnev's post, have the same interest in delaying a showdown that Kirilenko has. None of them is in a position of obvious pre-eminence that would give him any assurance of success if he did challenge either Brezhnev or Kirilenko. When he was still fully in command , Brezhnev made sure that he would not make the mistake Khrushchev had made, and allowed no one to acquire the public position of heir-apparent - not even Kirilenko, who has always exercised his power by manipulating the organizational levers rather than by building up his image.

The younger Politburo members also need as much time as they can get to develop their own networks of support, to establish their image inside the party elite as being associated with particular policies, to maneuver for position and to build up the alliances that would help them when Brezhnev finally has to go. Because of his state of health, that could happen at any moment, but he may also go on being propped up, physically and politically, for several more years. We just don't know, and it may well be that his doctors don't know either - to say nothing of his Politburo associates.

What we do know - and there is general agreement on this among Western intelligence analysts - is that if Brezhnev has to go soon, Kirilenko would step into his shoes. By the same token, if his departure is delayed for several years, the chances of a younger man coming to the top are much better.

What we do not know is what policies Kirilenko or whoever else succeeds him would follow, and there is general disagreement on this issue among Western analysts. Some believe things will go on just as they are, while others believe a harder, more conservative line will prevail on both domestic and foreign policy. Others still hold out hopes for a more liberal trend.