Contradiction in communist theory...
Even a cursory reading of Marx is enough to realize he was at the same time a staunch supporter and an enemy of democracy. As his texts can be found in paperback or on the Internet, a few very short quotes will suffice here.
Marx argues that democracy is the culmination of politics, and that a political emancipation is partial, selfish, bourgeois emancipation, the emancipation of the bourgeois. If, as he writes, "the democratic State [is] the real State", assuming we want a world without a State, we've got to invent a life with neither State nor democracy. However, when Marx presents democracy as "the resolved mystery of all constitutions", whereby "The constitution appears as what it is, the free product of men" (Critique of Hegel's philosophy of Right, 1843), he is opposing real democracy to the existence of the State, and therefore supporting democracy.
Besides, Marx was only indirectly addressing democracy through a critique of bureaucracy, and targeting politics through the critique of the State, particularly through its theorization by Hegel: "All forms of State have democracy for their truth, and for that reason are false to the extent that they are not democratic." (Id.)
One last quote, interesting because it was written decades after the early works, and by someone who was coming close to admitting the possibility of a peaceful transition to socialism: "One must never forget that the logical form of bourgeois domination is precisely the democratic republic (..) The democratic republic always remains the last form of bourgeois domination, the form in which it will die." (Engels, letter to Bernstein, March 14, 1884)
Intuitions leave much room for interpretation, and the context often blurs the message. To understand these conflicting views, we must bear in mind that, in the mid-19th century, a groundswell of social movements, from Ireland to Silesia, was pressing for radical democratic demands and social demands, both at the same time, combined and opposed, and this confrontation resulted in a critique of politics as a separate sphere. Let's not idealize our past. The same thinkers and groups often mixed these demands and this critique. The purpose of The German Ideology was to prove that history cannot be explained by the conflicts of ideas or political platforms, but by the social relations via which human beings organize their lives and, above all, by the material conditions of their lives. Those pages are to be read in connection with The Jewish Question, Critique of Hegel's Philosophy of Right, Contribution to the critique of Hegel's Philosophy of Law, The King of Prussia & Social Reform, the Theses on Feuerbach and other similar texts which address the democratic bourgeois revolution, but also the Rights of Man, and reject a revolution that would only have "a political soul". For example, Marx sees 1789 and especially the 1793-94 Terror in France as the culmination of political will that deludes itself into believing it can change the world from the top. There's little doubt that Marx wished to apply his "materialist" method not only to history, religion, philosophy and the economy, but also to the question of power and to politics as a field of special knowledge, as a separate science and technique. Yet at the time he was describing the political sphere as another form of alienation, he was also urging the completion of the bourgeois democratic revolution, and a few years later he became the editor of a liberal progressive paper, the Neue Reinische Zeitung, subtitled "Organ of Democracy".
The deeper the communist movement goes, the greater its contradictions are. Marx happens to be among the few thinkers who come closest to a synthesis and therefore inevitably combine its most opposed elements, the dimensions our movement is at most pain to reconcile. It's no accident that Karl Marx should have given one of the best insights into communism (in particular, but not only, in his early works) and welcomed the advent of capitalism as a world system.