Sentence:  ... Stalin was never able to monopolise Marxism, and the same deficiencies in theory which facilitate the claim of Stalinism to be a Marxism, allowed alternatives – even other <WSD>Bolshevisms</WSD> – to become subversive doctrines in relation to the reality of Stalinist power. 
Meaning of the word marked with <WSD> tags:  The Communist political ideology adopted by the Russian Soviet Federative Socialist Republic and the Union of Soviet Socialist Republics; Marxism-Leninism.