Sometimes in politics (though rarely in journalism) your sins will find you out. One of the lessons that Tony Blair says he learnt from his time in office was how his choices were affected and constrained by what he had said in opposition. He thinks he spent a lot of time undoing the effect of claiming that it was “standards, not structures” in education, reintroducing a previously abused internal market into the NHS, and now believes that he ended up suffering from Labour's successful pre-'97 taunting of John Major's Government as having been “sleazy”.

Of course, it all seemed like a good idea at the time, as now does the Conservative party's demand — backed by this newspaper — for a referendum to endorse ratification of what will become known as the Lisbon treaty. It is, is it not, a simple problem for poor old Gordon, trying desperately to justify to the electorate the breach of a promise made back in 2005? And it is, is it not, something of an open goal into which the Conservatives can keep scoring, from now to the next election? An election that, according to some of my more tribally Tory colleagues, is as good as in the bag.

I am not going lean against my mental five-bar gate, remove a straw from my mouth and give readers the wise shake of the head and the “Gordon bain't be as stoopid as he be painted” bit of political folk-wisdom. But I will remind them that there is something important being missed here.

This “something” is not the lack of popular interest in the issue of a referendum. It is the question of what, exactly, the next Conservative government would do about the provisions of the Lisbon treaty.

Dear reader, you know what Mr Cameron and company think about a referendum: they call for one. They demand one. They argue that life cannot go on without one. But what do they think of the Lisbon treaty itself, painfully negotiated by the 27 members of the European Union and recommended by the Prime Minister? Are they against all of it? Some of it? Practically none of it? What specific aspects of it do they reject beyond all compromise? We don't know.

Personally I support the Lisbon Treaty, since its big impact should be to make existing EU policy and practice more effective in the era of enlargement. Recently the Conservative Shadow Foreign Secretary, William Hague, argued that the union should “concentrate on the issues where the EU can really add value: global competitiveness, global warming and global poverty”. Exactly so, which is why, for example, the idea of a single high representative to speak for the EU to the outside world makes sense. This doesn't compromise the foreign policy of sovereign states, but does allow a co-ordination in precisely the areas mentioned by Mr Hague. Unless, of course, he has some kind of perverse interest in wishing the ends but always declining the means. There's a rude word for such tantalisers.

But it may be that the Conservative calculation is simply that their position on the treaty doesn't matter. They will make this an issue of abused trust, and fight the next election on Gordon Brown's nastiness, rather than on the EU itself. Then, the election won, they will cross the next bridge. By then, as Hague admits, the chances are that the Labour and Liberal Democrat majority in the Commons will, after some pain, have ratified Lisbon.

There are, however, two serious problems with these assumptions and both of them are linked to what I want to call the Great Malign Ratchet. It is very hard to campaign in a minor key, and — squeal as the Tories may and whatever the polls say — the voters are not that bothered by the referendum issue itself. Nor does the “trust deficit” transfer itself so easily from Blair to Brown; it is clear that Gordon has been donated different flaws to overcome. Increasingly, for the issue to have legs, the Tories will have to work with the anti-European lobby to suggest that the treaty itself is the work of Satan. They will have to build on Hague's claim that it will leave “power transferred from Britain to Brussels in spades and the EU fundamentally changed”, and for the worse.

Otherwise, why bother? Problem One is before the election, but after ratification. If the treaty is Luciferian, then what should the angels be offering in their next manifesto? It may require a memory larger than a Daily Mail reader's, but many anti-EU activists know that the Conservative Party in power has delivered precisely no referendums and plenty of big EU treaties, including accession, the single market and Maastricht — an approach summed up last month by the Liberal Democrat Vince Cable as “in office, supporting European integration, but in opposition, supporting the worst features of anti-European populism”.

Enter the Tory backbencher Bill Cash, MP, to general dismay and misplaced apathy. A few weeks back Mr Cash tabled an early day motion (essentially a petition) on Lisbon, with a killer last sentence, insisting that “the Prime Minister rejects the Reform Treaty on October 18 and holds a referendum before or after ratification”. “Before or after”. So presumably anyone signing this would want to see a Conservative prime minister taking the same attitude after winning an election and, that being so, would certainly want the reassurance of having such a promise included in the party manifesto. And, accordingly, one quarter of all Conservative MPs did sign the Cash EDM, including John Redwood, Michael Ancram, John Whittingdale and Iain Duncan Smith.

So there's the Great Malign Ratchet for you. The more the Tory leadership slags off the treaty to get one over on Gordon, the greater will be the activist demand that it promises to rescind ratification if it wins the election. But this, of course, it cannot do without risking leaving the EU altogether, which the British people will almost certainly not want.

But even if (and it's a big “if”) the Europhobes do as the Cameroonians may hope, and come over all trusting, bin their EDMs and go quietly until after an election, then there's still Problem Two. Which is that the political impact of rubbishing Lisbon will hold over well into any Conservative government. Governing from out of the soup of its own words, a Cameron administration would then have to decide whether to be true to its Europhobic rhetoric, or whether to make a break and try to achieve something in and through Europe. And if it's the former, David, then the Tories should never, ever be allowed anywhere near power.

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