In 2005, the French Socialists split over a new treaty for a European constitution; Mr. Hollande supported it, but Laurent Fabius, the current foreign minister, did not.
In January 1921, during a congress in Livorno, the left wing of the Socialists split away to found the Italian Communist Party (Partito Communista d'Italia, later Partito Communista Italiano [PCI]; now Democrats of the Left [Democratici di Sinistra]), which increased middle-class alarm.
The socialists were split: Jaurès insisted that no socialist could remain aloof on such a moral issue, while Guesde called the conflict a bourgeois squabble.
Today's American socialists are split on whether to revive a New Deal-style Democratic party or forge a new organisation.
But these efforts could not prevent the socialists from splitting along national lines too, and in 1910 the Czech socialists declared themselves independent of the Social Democratic Party.
The notion is particularly painful for Mr Hollande, whose Socialist party was split in the 2005 referendum on the EU's constitutional treaty, rejected by French voters.
In 2006 Cavaco Silva returned to politics with a successful run for the presidency, scoring a victory on the first ballot against a split Socialist ticket.
It ached again a few weeks ago when Socialist MPs were split in parliament over the most recent eurozone treaty: many abstained, and some voted against.
His Socialist party is split, one side favouring market-oriented reforms, the other holding fast to radical-left or anti-capitalist views.
And the French finance minister, a Socialist, may have split the diplomatic hair of the week when he discovered that his Austrian counterpart is from Mr. Haider's party.
