As I’ve seen it, it’s “they’ll marginalise themselves and become electorally irrelevant, so we won’t suffer another Tory government for a long time”.
Like Tories celebrating Corbyn becoming Labour leader. Sort of.
Not saying it’s a good take, just explaining what I think is the “logic” behind it.
It’s a difficult call for them. Firstly because they need to make an at least in appearance break from their failed government(s) which I’m not sure is possible with any of the likely leadership contenders.
Yes, it assumes two things: 1. Tories are bad (and/or I want Labour in government), 2. GEs are won from the centre.
Some truth in each, but taking them as axiomatic suggests a massive failure of imagination. It's got a whiff of Fifth Form Genius about it.