[PeterisP]

Why not?

If you have a one-party system, then all it means that the actual policy choices are made not by parties, but rather by factions or individuals within the one party, so if you want to change things, then the levers of change are obtained not by being a voter (or candidate) and having your party gain positions in the country but by being a party member (or official) and having your faction supporters gain positions in the party.