The Politburo was the supreme executive of the Communist Party of the Soviet Union (CPSU) and promotion to its ranks took entirely within that organization. Politburo members were Party members, but that fact does not really illuminate that much. There was a mediated structure which successive layers of the CPSU meetings would elect or nominate delegates who would repeat the process until one reached the apex of the organization. The actual process was much more nebulous in practice than the matryoshka doll process it was on paper.

The ideal place to start for describing this process is the CPSU Congresses. These were massive affairs that were supposed to convene every few years. The interval between Congresses varied within the lifespan of the USSR, but most of the post-Stalin period witnessed about five years between Congresses. The delegates to the Congresses came from the Primary Party Organizations, which were the major local CPSU organs who would in turn push delegates up the CPSU apparatus of regional and republic congresses and committees. The Congresses consisted of several hundred to a a few thousand voting delegates. Once the Congress convened, it would push through the agenda for the CPSU and USSR for the following years and climax with the announcement of the Central Committee of several dozen or so CPSU leaders.

The Central Committee (CC) in turn then elected the leadership of the Politburo (also termed Presidium under Khrushchev and not to be confused with the Presidium of the Supreme Soviet) and other executive branches. The CC also nominated the General Secretary of the CPSU, who for most of the lifespan of the USSR was the de facto head of state. The General Secretary was to be a first among equals among the CC and Politburo. The CC itself existed in an indeterminate netherworld between elections of the Politburo and the next Congress.

The process outlined above seems logical and almost democratic, but it practice becoming a Politburo member was anything but those things. For one thing, the outcomes for the Congresses were all but decided before they even convened. Although there was heated debates in the early USSR CPSU, the Stalin turn ushered in a trend in which CPSU politicking took place behind the scenes. Factionalism was not supposed to exist within the USSR but the CPSU was riven with rivalries and internal power blocs. The Congresses often existed to rubber stamp whichever constellation of political power that was in ascendancy. This arrangement of power was relatively simple during the Stalin period; Stalin was at the epicenter of power while a number of his chief lieutenants (memorably termed by Stephen Wheatcroft and Sheila Fitzpatrick as "Team Stalin") occupied a number of CC and Politburo seats. Things became more fluid in the Soviet executive process after 1953. Khrushchev and to a lesser extent Brezhnev tended to emphasize the collective leadership aspect of the Politburo's structure and all the General Secretaries post-Stalin had to rely upon allies within the CC and Politburo for political power. Khrushchev's fall from power took place within the structures of the CC and Presidium. Even though Khrushchev's forced resignation and retirement was the result of a conspiratorial coup, it had the appearance of legality and orderliness to it.

Khruschev's ignominious resignation was a symbol of the larger failures of the CPSU to form a coherent political system. The process of leadership and the mediating role of the Party seemed logically structured to outsiders. Congresses were streamlined affairs with massive announcements of ambitious agendas and a minimal amount of debate. The reality though was that the whole process was often extemporized behind the scenes as factions and blocs vied for power. Ordinary issues like succession became existential crises for those on the inside of the system as new power constellations formed and all parties tried to keep the appearance of normality to the Soviet public and the outside world.