Answer:
Gorbachev's decision to allow elections with a multi-party system and create a presidency for the Soviet Union began a slow process of democratization that eventually destabilized Communist control and contributed to the collapse of the Soviet Union.
Serving in the Russian Civil War before overseeing the Soviet Union's establishment in 1922, Stalin assumed leadership over the country following Lenin's 1924 death. Under Stalin, socialism in one country became a central tenet of the party's dogma.