Allow me to expand/explain further:
I live and vote in Berwick-upon-Tweed constituency, which went to the Tories in 2015, having been represented by Libs/LD (well, Alan Beith) for the longest time before. Labour has been a distant third for ever - this isn't Wansbeck or Blyth Valley. LD was the best way of Not Getting A Tory.
Clegg shafted us in 2010, by following his ego into coalition, rather than any other form of arrangement. I have a postal vote, so at the point I voted that year no indication had been given that the LDs would prop up the Tories.
Not enough folk will ever vote Labour to make a Labour vote a worthwhile way of Not Getting A Tory. FPTP is a sod for that sort of thing.
The Labour PPC for some years is/was my local county councillor, who I have gradually learned is not always a straightforward as he makes out, losing the trust of a number of folk locally.
Corbyn Bros: Piers and his eejit weather ideas I have long known about and thought him a waste of space; Jeremy, well, what can I say? I moved on the fringes of some of those lefty circles in the '80s as he first became an MP, and while the whole bunch of them were notable for arguments about ideological purity rather than anything resembling competence, he always came across as especially contrary and avoiding being seen as competent.
When Corbyn, J, became leader of Labour I predicted a total balls up, and we got it: imagine a Dennis Healey, Robin Cook, Nye Bevan, any of the heavy-weight bruisers of the past, even Blair or Brown, opposing May or Johnson and think of the mess they would have made of them. What did Corbyn do? Naff all, as expected.
Even folk of a lefty stance are not required to believe in Corbyn, especially as some of us know too much.
The anti-semitism debacle was also pretty predictable, as that strain has been around in some sections of left wing politics (and other parts of the political spectrum too) as far back as I can recall.
