For many years, he was considered Khrushchev's likely successor but even before his mentor's removal from office, Kozlov's position had been undermined by the effects of his alcoholism; in the spring of 1963 he was replaced by Leonid Brezhnev as Secretary of the Communist Party Central Committee. At the time of his removal, Kozlov had already suffered a stroke, and he died shortly after his removal from office. He was, in 1992, deemed partly responsible for the June 1962 Novocherkassk massacre.