From Revolutionary Russia, 1891-1991: A History, by Orlando Figes (Metropolitan, 2014), Kindle Loc. 4437-4453:
Who knows what would have happened if Andropov had lived longer. Perhaps the Soviet Union might have undergone a more gradual transition from the old command system, modernizing the economy without relinquishing political controls, as done by the Chinese, though one wonders if this could have been achieved given the extent of the Party’s opposition to de-collectivization, the key to China’s revival. As fortune would have it, Andropov became terminally ill with kidney failure only nine months after coming into power and died, at the age of sixty-nine, in February 1984. From his death-bed in hospital, he wrote a speech to be read out at the Plenum of the Central Committee recommending Gorbachev to succeed him. But the crucial paragraph was cut by the old guard in the Politburo, opposed to reform, who on his death voted to replace him with Chernenko. Within weeks of his appointment the 73-year-old Chernenko became terminally ill. The Bolsheviks were dying of old age.
Gorbachev bided his time—careful not to alarm the old guard by giving the impression that he might go on with Andropov’s reforms yet building his support in the Central Committee and increasing his prestige by trips abroad, where he impressed the British leader, Margaret Thatcher, in particular, on a visit to London in December 1984. Such impressions were important to the Soviet government, which needed Western credits and disarmament. They no doubt helped him make the deal with Gromyko, the Foreign Minister, by which Gorbachev agreed to promote him to head of state (Chairman of the Presidium of the Supreme Soviet) if he supported him to succeed Chernenko as the Party’s General Secretary. It was the backing of Gromyko, a veteran Brezhnevite, that tipped the scales in Gorbachev’s favour in the Politburo vote on Chernenko’s death the following March. There was no battle for the leadership: the old guard simply stepped aside to let in a younger man.
The selection of Gorbachev was arguably the most revolutionary act in the history of the Party since 1917. Had the Politburo known where he would lead the Party in the next few years, it would never have allowed him to become its General Secretary. But at this stage Gorbachev’s intentions were still far from clear.