Final answer:
The policy that allowed for political openness and criticism in the Soviet Union is known as glasnost, introduced under the leadership of Mikhail Gorbachev as part of his reform efforts that also included perestroika.
Step-by-step explanation:
The process whereby the Soviet Union opened up to grant modest political debate and criticism was known as glasnost. This policy was part of the larger reform effort led by then Premier Mikhail Gorbachev, who, after taking office in 1985, recognized the urgent need for change within the Soviet system. Alongside glasnost, Gorbachev also introduced perestroika, a restructuring of the Soviet economy. While perestroika sought to incorporate market-like reforms to revitalize the economy, glasnost allowed for a degree of freedom of speech, including the ability to openly criticize the government without fear of state retribution. These reforms ultimately contributed to increased political openness and played a role in the eventual fall of the Soviet Union by 1991.