A Party Divided

In some quarters, the European Union is viewed as a conspiracy of French socialists. And indeed, France's Socialist Party (PS) has traditionally been one of the biggest boosters of the E.U. That's why the current polarizing battle within the PS over a referendum, scheduled for Dec. 1, to accept or reject the E.U. constitution is so puzzling.

Last week, the standing-room-only crowd that packed the Centre Rabelais theater in the southern French city of Montpellier went wild as Socialist Party leader François Hollande and former Finance Minister Dominique Strauss-Kahn extolled the merits of the treaty. Mention of party...