When campaigning began for Thursday’s Irish referendum on the European Union’s Lisbon treaty, few thought there was the remotest chance of a “no” vote. The massed ranks of the Irish Establishment lined up in smug anticipation of a resounding victory for the “yes” campaign. Brussels regarded the referendum as a mere diversion, confident that Irish voters would apply the rubber stamp in the appropriate place. Even the bookies thought there was more chance of a Shergar winning the Derby.

Whatever happens this week, those cosy assumptions have been thrown out of the window. Alone among the Irish media, this newspaper, which is one of the biggest selling broadsheets in the republic, argued the case for a no vote. The latest opinion poll, showing the no camp in the lead (although admittedly with a large number of “don’t knows”) has alarmed the Establishment. Could it be that Irish voters will do the right thing, which happens to be the exact opposite of what Brussels wants?

That they should reject this treaty is not in doubt. In Britain and in other European countries, the constitution – in all but name – is being foisted on citizens without an opportunity to have their say. Gordon Brown insisted wrongly that Labour’s manifesto commitment to hold a referendum on the constitution did not apply to the Lisbon treaty. But parliament has so far failed to hold the government to account and the treaty is making its way into British law. Only the Irish can stop it by sending Europe back to the drafting board. This, of course, is the scare tactic adopted by the yes campaign. The European Union, they say, will be thrown into chaos by an Irish rejection of the treaty. It is a desperate and dishonest tactic. According to Ireland’s independent referendum commission, in the event of a no vote “the EU would continue to operate under its present rules”. The chaos theory is bogus.

Anybody who has tried to plough through the reform treaty will quickly realise that it has met the test set by Giuliano Amato, the former Italian prime minister, who said it “should be unreadable”. Valéry Giscard d’Estaing, the former French president and architect of the constitution on which the treaty is based, said “public opinion will be led to adopt, without knowing it, the proposals that we dare not present to them directly”. Last month in Ireland we published the treaty in its entirety in order to demonstrate how successful that strategy has been.

Nobody should sign up for something they do not understand. But there are other reasons for rejecting the treaty, not least that it is a reheated version of the constitution thrown out by French and Dutch voters in their referendums in 2005. Those voters are not being given the chance to decide again. If Ireland rejects the treaty this week, Brussels will no doubt find some way of getting around it. That battle is for another day. The first requirement is for a no vote this week. It is one occasion when many of us will have no hesitation in saying: come on Ireland!