A French "non", followed by a Dutch "nee", would certainly be a shock to the system, but the indications are that EU leaders will respond by calling for the ratification process to continue – insisting that the outstanding referendums go ahead.
Certainly, if the Financial Times is any guide – and the paper usually has a good inside track record - the emphasis will be on downplaying any sense of crisis, with calls for a "cooling-off period".
Already scheduled is the June European Council, to be held on 16-17 June, and the likelihood is that there will be no formal decisions until then. Member state leaders, it appears, have been schooled to avoid alarmist rhetoric, and will reserve their comments for the Council.
By then, it is hoped that the "colleagues" will have been able to craft a common position, reflecting the line being offered by Juncker and Barroso that all other member states should have their say on the constitution.
The Commission's line is that: "The procedures have been completed in nine countries representing over 220m citizens - that is almost 49 per cent of the EU population," on which basis the ratification procedures should go forward.
That means the referendums in Britain, the Czech Republic, Denmark, Ireland and Poland should go ahead as planned. The next poll will be the Danes, scheduled for 27 September, with the whole ratification process continuing until November 2006. Only then would there be a special summit to discuss what to do with the refuseniks.
However, this carefully crafted exercise in damage limitation could be blown apart if there is a "Grand non" and Chirac throws his toys out of the pram, declaring the treaty dead in the water.
That apart, EU officials are still hoping that if most countries ratify the treaty, the refuseniks could be told to hold second referendums.
In France, presumably, this would be after Chirac had ditched Raffarin and put in a new prime minister, having blamed the "non" on the unpopularity of the previous government rather than with dissatisfaction over the treaty. It could even be held after the 2007 presidential elections, in which case L'escroc would be history as well, leaving his successor a clean slate.
All this, of course, is highly speculative. Although polls in Denmark currently favour the constitution, sentiment could – and is likely to - change as the referendum date approaches. The Danes could deliver a "no". Britain, on current form, will almost certainly say "no", and it would be a wise man (or even person) who made any predictions about Poland, Ireland and the Czech Republic.
By the end of 2006, the situation could be inestimably worse for the "colleagues". Not least, the "yes" campaigners in the remaining referendums may have been deprived for their most potent argument – that their countries will be "isolated in Europe" if they say "no". Thus, instead of two, the colleagues could be facing six "noes".
That said, the EU has in the past shown an extraordinary capacity for survival, weathering seemingly terminal crises. Therefore – Chirac apart – the chances are that the damage limitation exercise currently being constructed will buy time for the project, while the colleagues work out a more creative rescue plan.