What political idea in Russian history does Old Major represent?

Old Major symbolizes the Marxism–Leninism of the Soviet Union. He provides the intellectual foundations of the philosophy of Animalism, which he genuinely believes will liberate the animals from oppression at the hands of their human masters. Although Old Major is largely presented in a positive light, his ideas contain within themselves the seeds of the future dictatorship established at Animal Farm by Napoleon. For one thing, Old Major's political ideas are rather naive and simplistic. He seems to believe that once human power is overthrown, then all will be well. When the animals take control, there will be complete freedom for all; everyone will work together for the common good and no one will dominate or control anyone else. If nothing else, Animalism means equality.
The problem is that Old Major's ideas are, at best, unrealistic. His idealization of animals means that he's blind to the prospect that they too possess all the worst traits of humans. Contrary to what he believes, there is no true brotherhood of animals. Once the humans have gone, and the animals have taken over, all the old problems will still remain much as before. Orwell is satirizing Marxism–Leninism here, especially as it was put into practice by Stalin. What started out in theory as a perfectly admirable political philosophy, one devoted to liberating the oppressed masses, has degenerated in practice to a rigid ideology that enslaves and terrorizes the very people whose interests it's supposed to represent.