“Would the situation have changed much since Robert Michels wrote his book on political parties, based mainly on the SPD”
Yes, there could be some relevant material in this. Will have to get a copy and look through.
In the writings of Kautsky he thinks that working-class participation in parliamentary politics would have a ‘prefigurative’ effect, to use some of today’s parlance. I just wanted to see to what extent this actually follows through to the internal structure of the SDP and USPD.
Incidentally, I’m wanting to find the same kind of information about the Canadian ‘impossibilist’ parties too.