LONDON (Breaking Views) - Michele Alliot-Marie is worried that a French vote against the proposed EU constitution could cost a million lives.

The French defense minister told supporters that without cross-border co-operation, terrorists would find it easier to use weapons of mass destruction.

That sounds like a bit of extreme political rhetoric. But a strong French rejection could reduce one life expectancy, that of the euro itself.

France will hold a referendum on the proposed EU constitution on May 29. The latest opinion poll shows a 55 percent to 45 percent majority against ratification, with 22 percent of the voters undecided.

The Netherlands will hold its referendum June 1. The latest opinion poll shows a 60 percent to 40 percent majority against.

To be sure, the euro has already fallen to a seven-month low against the dollar and the spreads between strong and weak eurozone governments have widened. The fear that the EU is about to enter one of its initiative-freezing periods of internal crisis has probably contributed, along with growth worries.

The moves are probably an adequate reflection of the most likely result of Sunday's French constitutional referendum, a narrow negative majority.

But suppose the "no" vote wins big, by something like 60 percent to 40 percent. And suppose the Netherlands follows on Wednesday with an even larger rejection.

That could cause something more serious than the usual EU pattern of navel-gazing followed by a vague compromise. The idea that the euro could be dissolved might start to look like a practical possibility.

The unsustainability of the euro has been a topic of dinner table conversation from long before the single currency was created. Many observers feared that the independent central bank would not be able to keep sufficient control on the member nations' fiscal policies. High debt loads might force countries to drop out or be expelled.

The counter-argument to such pessimistic speculation was vague but powerful. The momentum towards a single Europe would keep the countries in line. The EU constitution was supposed to be an important sign of that progress.

Europe will not fall apart without the constitution, despite its supporters' more hysterical arguments. But politicians in the overly indebted member countries will pay attention to the voters' strong anti-EU mood.

That could lead them to think twice when it next comes time to make valiant budgetary sacrifices for sake of European unity. Leaving the currency could accurately be portrayed as the democratic choice.

Breakingviews is Europe's leading financial commentary and analysis service. Its team of financial journalists comments on the most important financial stories of the day, as they break.