Why the time limits? Even within them: Thorstein Veblen, John Dewey, Rosa Luxemburg, Marx and Engels, Eugene Debs, Frederick Douglass, W.E. B. DuBois, E. Cady Stanton & Susan B. Anthony. I would also give credit, though not sympathy, to bourgeois theorists of the era who were right about modern power's dynamics, but not its ultimate meaning: Mosca, Pareto, Bernays, Lippmann, Schumpeter, Lord Acton.
All these figures (and many others) blow Lenin's doors off in terms of political theory staying power.