His fans here are far better qualified to answer than me, but I was under the impression Corbyn (and more importantly his manifesto) were doing rather well in 2017. The support fell off a cliff once the legendary Fence of Brexit Ambiguity was wheeled out and every PMQs was full of Brenda from Barking’s bus timetable etc rather that the economic and social catastrophe being metered out on the UK by the Tories and the far-right. Labour ended up way out of step with all the other progressive left parties, so my analysis isn’t entirely without evidence. Again I blame Duffygate for this. The party has been neutered ever since.
FWIW I do increasingly think Labour should fight elections from the left (i.e. Corbyn was right in that), but also with a shared platform of electoral reform with the other non-Tory parties as PR is the only hope, the only way forwards. The more I look at it the more I’m thinking the endless dull grey corporate suits bur, long ing up focus-group-defined Tory-lite policies just doesn’t mean anything to anyone. I suspect Labour need to grasp they can never represent folk like me and get back to core function of forcefully and unashamedly representing unionised mass labour, the working class, the inner cities, zero hour contracts, the unemployed etc. There are others here who understand the stats far better than I do, but I’m increasingly coming to the conclusion that this, and obviously the pushing of real electoral reform, is the only hope in hell for the UK. Let the LDs or Greens look after the likes of me, I fully understand I am a middle-class liberal with all the baggage that brings! Labour need to get back to their core early 20th century functionality and representing those who currently so desperately need it.