Lazar Kaganovich
At the conclusion of the Congress in March 1939, Zhdanov was promoted to full membership of the Politburo. He was still one of four secretaries of the Central Committee - the others being Stalin, Andrey Andreyev and Georgy Malenkov - but Malenkov was not a Politburo member of the Politburo, which meant that Zhdanov had replaced Lazar Kaganovich as Stalin's deputy in the party apparatus and appeared to be his most likely successor.