The question now is what happens next. Domestically, I doubt that the party will have a big row about Europe—it is too disciplined, too eager for power for that.
In European terms, the question is always put as does Cameron have the stomach for a battle with Brussels. But it is worth flipping this around: does the European Union want to pick a fight with Britain? It is reasonable to ask if other European leaders will be prepared to offer Cameron enough to square his party and his country to Lisbon. If they don’t, the pressure will build on Cameron to obstruct until he gets what he wants the next time that treaty changes are required.