"When the facts change, I change my mind," declared the economist John Maynard Keynes. It's not an unreasonable approach and it enables me to predict confidently that, as matters stand, the Conservative Party will not win the next election.
Sure, I'll vote for it, but why would anyone else? Yes, Michael Gove's education reforms deserve your support, but perhaps it's too late for your children, and while you approved of the government's plan to slash the welfare bill, maybe you were less impressed when you realised it was only to the equivalent of a pre-tax salary of £35,000.
Or perhaps you care deeply for the fate of the armed forces and resent your hard-earned money supporting other countries' space programmes – let's not go there.
There are many excellent things to be said about the Conservative contribution to this Government, but it is against a background of unremitting financial gloom. For anyone in their 50s, it will last the rest of their working life and the whole of their retirement. That realisation poisons the political well. But sometimes, a government can find an overarching theme that transcends the weary cynicism of "It's-the-economy, stupid".
In 1981, when Mrs Thatcher looked as certain to be a one-term Prime Minister as David Cameron does today, it was the invasion of the Falkland Isles. It seemed that England itself had been invaded, as indeed in a sense it had. But should that thought bring any comfort to David Cameron today?
Earlier this month, the government lost a division in the House of Commons on an opposition motion which it should itself have tabled – that the EU budget should not just be frozen but cut.
Given that the EU is so financially corrupt that for the 18th year running the auditors have refused to sign off its accounts, what Conservative could have objected to that?
Now, I accept that on our present terms of EU membership, it would be impossible to achieve, but there would have been nothing wrong with pointing that out, while still seeking the best deal available. Instead, the opening bid in our budget negotiations is to simply veto anything we dislike, and if that happens the figures for 2013 will just be rolled over in 2014, with an extra 2% added for inflation.
That's hardly Mr Cameron's fault, but by apparently accepting the rules of the game, he nevertheless runs the risk of being blamed.
And yet that vote, humiliating though it was, offers the very real prospect of the Conservatives winning the next election after all, because there has been real movement of late on the party's position on Europe – even if it seems driven more by pragmatism than principle.
No longer is it a question of "There will be no referendum because we think we should stay in Europe". Now, it appears the next Conservative election manifesto will contain a commitment to renegotiate the terms of our EU membership, with a referendum on whether Britain should accept the new package or leave the EU.
What has the Conservative Party to lose? It does what is right, it does what the polls show people overwhelmingly want and it shifts the ultimate responsibility for the outcome to where it should lie: We, The People.
But it doesn't stop there. By invoking the procedures of Article 50 of the Lisbon Treaty, which provides for the secession of participating states, it would meet UKIP's central demand that the British people should have a referendum on the question of continuing membership of the EU.
Of course, David Cameron's analysis of what is wrong with the EU would have to accord with that of the UKIP leader Nigel Farrage, but would they really be so far apart? My reading of Mr Farrage is that he is not out to destroy the Conservative Party, but wishes to save his country. That is a profoundly Conservative position.
Depending on how you read the figures, UKIP stands to lose the Tories between 20 and 80 seats at the next General Election, without winning one parliamentary seat for themselves.
In short, the facts have changed. Twelve months ago, six months ago, there was no principled position on which the Conservative Party and UKIP could make common cause. Now both parties are committed, it would appear, to a referendum on continued membership.
The paths the two leaders have taken to reach that conclusion may have been different, but it's the destination that matters.
So will Mr Cameron be telephoning Mr Farrage any time soon? Who knows? But faced with electoral extinction, or the near certainty of victory, I know what I would do.