The intervention by Jacques Chirac, French president, in support of the European Union's draft constitutional treaty in Thursday's televised debate may come to be seen as a turning point, whichever way France votes in the referendum of May 29.

If voters say "yes", there will be no shortage of presidential aides to hail their boss's appearance as a decisive event that turned the tide after a month in which more than a dozen opinion polls have predicted a "no" vote. If they reject the constitution, the debate will be a rich source for analysts seeking deeper explanations for why the French, whose political elites have done so much to shape the EU, have turned against their creation.