Having thought more about this, I think I can see a plan:
1. Boris is going to bring something back from Brussels that looks and smells just like the original withdrawal agreement - but with some backstop related tweaks. It won't be removed - it might be reworded.
2. The above agreement is going to look so close to the original one, he needs a new session of Parliament to avoid the Speaker saying that this is more of the same!
3. Of course, the ERG (and Farage) will be furious with this, but they simply don't have the numbers to do anything about it and because this process has spooked everyone so much it becomes this agreement or a no deal Brexit. End result, Parliament reluctantly votes it through - just in time for 31 Oct.
4. Boris then calls a GE on the back of being the PM who got Brexit done.
This whole plan assumes that most traditional Tories will buy anything from Boris, so long as he does that Boris thing of punching the air and mentioning positive spirit etc. etc. Also, No. 10 is already rolling the pitch by talking down any expectation of changing anything more than the backstop (which is a big demand of the ERG and Farage).
There you go, until my next theory
