PARIS — When Nicolas Sarkozy became president of France, he declared that his country was back in mainstream Europe. Since then, Sarkozy has thrown himself into the European political fray.

His energy — combined with the negotiating talents of German Chancellor Angela Merkel — overcame antagonism toward the new reform treaty that EU leaders just ratified in Lisbon, putting the European Union back on its feet after two years of crippling indecision.

This triumph, however, marked only a partial return by France to the European fold. The French must now resolve their own ambiguous attitudes about Europe, which have affected national policies for decades.