Champagne corks were popping in the French presidential suite last night after the socialists won a commanding parliamentary majority in Sunday’s elections. Following nearly a month of walking a fine line between drumming up support for his socialist party and placating nervous conservatives and investors, Hollande’s Socialists have finally emerged with a clear victory.This is no small matter. The French system has one of the most powerful presidencies in the world, thanks to Charles de Gaulle, who was sick of decades of weak French governments and wanted to be able to rule the country in his own inimitable (and highly effective) way. When a French president also has an absolute majority in the national assembly, as Hollande does now, he has almost unfettered authority.Under ordinary circumstances, this would be an enviable position for an incoming president. Now, however, the economic situation in France and in Europe is so dire, and France has so little wiggle room before markets start to punish its bonds and banks, that the new president is going to have his work cut out for him. Can he please the voters who bought into his campaign of resisting financial markets without driving the investors and lenders away that France needs? The celebrations are going to be short-lived.