Marx wrote the Communist manifesto with Engels who has as much to do with Marxism as Marx. They were both the farther of communism (the only reson they disliked the term socialism is because in that day and age it was to closely associated with social democrats (or watered down communists who believed in capitalism in reality), and plus they had an obbsession with dialectics).
Marx hated anarchists, anarcy is the idea that there should be no state, no structure, no central government. The end result of communism is wholly different to that - the term 'withering away of the state' by Engels wasn't meant to be taking as the state actually withering away, as in dissapearing - this is a crude and opportunist intepredation of Marxism - withering away was meant in the first instance as a response to the "abolishing" of the bourgeois state, or abolishes the state as state after the proletariat revolution.
After the revolution the idea then being as a communist state becomes more and more developed there will be little need for elected officials (democracy) since it will be a system of distribution - and no decisions will need to be taken, only managment of the system will be needed...thus in this sense the withering away of the state is inevitable in Marxist doctorin (this is a VERY simplistic analysis of the theory of withering away of the state, and i mean simplistic - it was based by Engels on the Paris Commune of 1871, and again the term 'withering away' is in line with Marxist dielectics and is unfortunate because it sounds a lot like the anarchists idea in words, but not substance.)
What the Soviet Union did under Lenin was going in the direction of Marx communism, Marxist-Leninists are pretty much the same thing only with revolutionary theory mixed in (the problem being the revolutionary theory effects the state greatly after the revolution, hence such things as the seceret police, and the civil war), anyway the system of the Soviets was the closest system we will ever have towards the 'dictatorship of the proletariat' or to put it in less offensive and less dialectic terms 'democracy of the proletariat' - it was the system of democracy for the workers, for every 10,000 workers per say - there would be one representative in the Soviet assembly, the reprentative would have to be a worker in the factories they represented and not some educated person who would never have stepped foot in the factory and not understand worker culture. The idea being they would represent the workers and not their owners interest, if u didnt work, u didnt vote, if u owned the means of production - u didnt vote (although this point is void since Lenin burned all land deeds effectivly eliminating the capitalist class, this was not a good move by Lenin, especially when it came to organising the NEP)
Anyway in the Soviet Union under Lenin they were working towards a communist state inviseged by Marx, it wasnt perfect and may not have worked even if given the time to develope - but when Stalin took power he produced a system totally alien to communism, he wasnt a communist or socialist - his 'Socialism in one state' is contradictory to every marxist principle and Marxist-Leninist system. In terms of communism as an experiment in Russia, only 1917-1924 should be studied!
peace
MX!