France’s opposition Socialist leader has pledged a radical shake-up of the divided party, with US-style primaries to pick its next presidential candidate.Last time round, the left’s big hope, Segolene Royal, failed to beat Nicolas Sarkozy. But activists, gathering for a summer conference, hope root and branch reform will produce a very different result in 2012. Martine Aubry, who defeated Royal in a leadership vote last November, rallied the troops with calls for changes from A to Z. That is music to the ears of Arnaud Montebourg, one of the Socialists’ rising stars, who threatened to quit the party unless the principle of primaries was accepted. For him, the overhaul promised by the leadership is nothing short of revolutionary, with the creation of a new Socialist Party the reward. It has all got the gathering at the Atlantic Port of La Rochelle off to a buoyant start but some squabbling is set to continue. The big question now is whether the primaries should be open to others on the left or only Socialist Party members.