I happened to read the Wikipedia article on the Paris Commune recently, and it mentioned that Marx and the anarchists split over whether the Commune should have assembled a more centralized, ruthless mode of operation. It seems likely to me that the rather divergent ideals of leftist government would separate into different ideologies even without a concrete revolutionary scenario, but I imagine that (if Wikipedia can be trusted on the Commune's import to the bifurcation) leftism could have fractured somewhat differently in different circumstances.