Imagine that David Cameron pulled this one off and held a referendum on EU membership with two options on the ballot - a renegotiated settlement acceptable to his lot and outright withdrawal.
That would unite the left since some factions inexplicably decided that Europe was a bulwark against Thatcherism.
Oddly, several years later Thatcher herself seemed to begin to agree with them.
For if the only alternative were whatever could be sold to the remains of the Conservative Party, then the only viable option would be whatever else were on offer - namely withdrawal.
This would be advocated in the strongest possible terms by the whole of the left.
It would be the Thatcherites who would be campaigning to stay in.