There is a time when one's duty to one's nation supersedes loyalty to narrow party interests. Being a Conservative isn't a matter of membership of a closed club, it's a state of mind. If you believe in virtue, honour, the reward of merit, equity and justice and the freedom of the British people to create voluntarily bodies to exercise collective authority, then you're a Conservative. If, like Sir Patrick Cormack, you can say "I've always taken the line it's country-constituency-party, in that order", then you're a Conservative.
Cameron's plea today will be to vote for him to get rid of Labour, and no doubt most of us will agree, perhaps reluctantly, to do so, for Labour is a pernicious evil far worse than anything that the Conservative Party can visit upon us.
But please don't phrase it as a patriotic duty. It isn't. It's a moral duty.
My patriotic duty is to campaign for a referendum amongst the people of Britain to determine the terms on which we should remain in the EU. Or not. And if this means making life for Cameron as uncomfortable as possible, so be it.