Though Lysenko remained at his post in the Institute of Genetics until 1965, his influence on Soviet agricultural practice had declined after the death of Stalin in 1953. Lysenko retained his position, with the support of the new leader Nikita Khrushchev. However, mainstream scientists re-emerged and found new willingness within Soviet government leadership to tolerate criticism of Lysenko, the first opportunity since the late 1920s. In 1962, three of the most prominent Soviet physicists, Yakov Zeldovich, Vitaly Ginzburg, and Pyotr Kapitsa, presented a case against Lysenko, proclaiming his work as pseudoscience. They also denounced Lysenko's application of political power to silence opposition and eliminate his opponents within the scientific community. These denunciations occurred during a period of structural upheaval in Soviet government, during which the major institutions were purged of the strictly ideological and political machinations which had controlled the work of the Soviet Union's scientific community for several decades under Stalin.