In Sweden, in the past 50 years, people with ”new” or fringe opinions have successfully started parties, and won seats in either the national or EU parliament, on these issues:
- Christianity - Environmentalism - Racism/populism - Internet freedom/privacy - Feminism - Racism/populism, again
Most of these have had their issues adopted by larger parties through triangulation, and thus shrunk away to nothing, while others persist to this day (christianity, environmentalism, racism).
I think if you tried to start a new labor party in the UK today, you should not expect to win any seats. Likewise if you attempted what the Swedish Feminist Initiative did. But I hope I’m about to be proven wrong on the first point.
Admittedly there is a bureaucratic logjam in the UK that hampers any progress but I don't see that going with fptp, I'd anticipate it getting much, much worse under prop-rep.
https://phrack.org/issues/72/19#article
I exclude the RE guys who are undoubtedly extraordinary.