Now we can safely drop the fiction of a "primary of the left," of une belle alliance populaire. This is a Socialist primary, pure and simple. And yet its outcome is unlikely to settle the future of the Socialist Party--if it even has one. More than anything else, it will consecrate the deep split between the Socialists who see their party as a party of government and those who see it as a radical alternative to the status quo.
If Valls, who stands for the party of government but has lost favor even with many who might normally be his natural allies, loses, he will still remain their heir apparent to Hollande as the most "realistic" of the Socialist leaders, although challengers for this position will undoubtedly emerge.
If Hamon wins, he will have a leg up among those who wish to redefine the party by reinvigorating the utopian side of its message. The campaign has effected something of a metamorphosis in his public image, but it's hard to gauge how much real support his underlying "eco-socialist" message really commands. For now he is THE alternative to Valls, but his program of universal basic income, limits to growth, and revised relation of work to human dignity remains a bit too distanced from the pragmatic world of French political discourse, for better or for worse. He will nevertheless have to be reckoned with.
Of course there is always the possibility that the winner of this primary will fare better than expected in the coming presidential race. Fillon's apparent collapse once again reshuffles the deck. If some surprise befalls Macron, the new chou-chou of the hour, who knows what could happen? But let's see where things stand after the results come in a couple of hours from now.