The notion that knowledge, skills, ideas, tactics, repertoires, personnel move from one (failed or successful) issue/movement to another. So, for example, the UK NVDA climate movement soothed itself after its collapse in 2010-11 by moving into the Occupy “movement” and thinking that progress was still being made. So it goes.
Please note – am not saying spill over doesn’t happen, (clearly it does) or that it is a ‘bad thing’. Just saying that it can be used as a way of avoiding the subject…
There’s a section on it in an encyclopaedia of social and political movements.
see also innovator movements, spin-off movements