On the contrary, I think that in countries were parties only purpose is to run campaigns, these organizations aren't really parties in the proper sense, especially if candidates are able to raise money independently of the party. "Parties" are more or less ad hoc fundraising committees with very little popular participation. That's why most people who claim they are Democrats or Republicans do very little other than vote, or at most, donate some money. Parties, imo, are conduits for grassroots mobilization. They were, at one point, social clubs as well as political organizations.
In a one-party state, there was a typically a different command structure than the ordinary hierarchy of the state. Through party rules, party officials could resolve many problems through local government, even though many of the institutions formally were not under the control of local government. But because they were led by party members, these individuals were subject to the discipline of local party organs. Indeed the CPSU relied on local and regional party organs to coordinate the economic system even though the local and regional governments didn't have this authority, per se.
Also the party system created a demanding civil service qualification system where only the most qualified, hardest working civil servants who had worked for a decade or two were admitted into the party. In this way also the state could ensure ideological correctness and competence among its managers and administrators.