The comparative study of political parties has always had difficulty with the Communist Party of the Soviet Union and those other ruling communist parties modelled upon it. This is because our approach to political parties has been overwhelmingly shaped by the liberal democratic experience within which the discipline of political science developed. As a result, the concepts used to understand parties are well adapted to those parties which operate in such systems, but have less immediate relevance to those bodies which call themselves parties and which operate in non-liberal-democratic systems. The notion of the one-party system was the framework political scientists used to try to come to grips with the vast array of non-liberal democratic parties, but this alone was unsatisfactory; it could not encompass the vast range of differences between those parties ruling in the communist world and single-party regimes throughout much of the third world.

The chief area of difference between the ruling communist parties and those of the non-communist third world usually is seen in terms of the degree of control which the party seeks and is able to exercise. The tight control exercised by the communist party is contrasted with the looser degree of control enjoyed in the non-communist world, a dimension often seen in terms of the much more limited scope for opposition which existed under communist rule. The distinction between narrow and broad single parties, with the latter being much more relaxed about factions and internal disagreement than the former, is another aspect of this dimension of control.