Paris - The French Socialist Party and its self-appointed diva, former presidential candidate Segolene Royal, are fighting for their political survival, and it is not a pretty sight.

After last weekend's bad-tempered party congress in Reims failed to choose a leader or a platform, the party's more than 168,000 dues-paying members are to vote for a new head on Thursday - and if necessary, on Friday.

The vote will be decisive for Royal's political future, and could also be critical for the chances of the Socialists to unseat President Nicolas Sarkozy in 2012.

In the election, Royal is facing off against the mayor of Lille, Martine Aubry, and 41-year-old Benoit Hamon, but the deep divisions that emerged during the Reims congress left many wondering if the French Socialist Party is too dysfunctional to exist.

"If it cannot surmount this crisis, the Socialist Party is in danger of dying," influential Socialist lawmaker Pierre Moscovici warned, while outgoing party head Francois Hollande complained, "I'm ashamed of the Socialist Party."

"Rarely has the democratic process ... come up so empty," the left-leaning daily Liberation commented on the congress.

The violent infighting may have been inevitable, as the Socialists seek to redefine themselves in a political environment transformed by the hyperactive and unabashedly populist Sarkozy, a popular anti-capitalist movement run by a media-savvy young postman, and the deepening economic crisis.

Sarkozy outmanoeuvred the Socialists by appointing its most popular politician, Bernard Kouchner, as his foreign minister, naming a number of minority ministers and junior ministers to his government and resorting to the traditionally left-wing strategy of state intervention to combat the financial crisis.

And on the party's left, the politically adroit postman, 34-year-old Olivier Besancenot, has been drawing away supporters who are discouraged by the Socialists' constant bickering and their inability to formulate a coherent strategy to counter Sarkozy.

In addition, several high-profile politicians left the Socialist Party last week and announced they would establish another anti-capitalist party, the Party of the Left, which is to be modelled on Germany's Die Linke.

The problem facing the Socialist Party is that, as unemployment rises in the coming months and the economic news worsens, it will have to find a way to keep its leftist fringes loyal without at the same time alienating centrist voters who do not like Sarkozy.

This is no simple feat, and is certainly one big reason the party is having trouble finding its way - but certainly not the only one.

The split within the party began in the early days of the 2007 presidential campaign, when Royal thrashed a number of the party's old guard - former prime minister Laurent Fabius and current International Monetary Fund head Dominique Strauss-Kahn - in the primary.

She then horrified the party's "elephants" by suggesting an alliance with centrist Francois Bayrou and his Modem party.

Royal has now repeated the call for a left-centre alliance, saying that the party must "open its doors and windows" if it wishes to have greater appeal. She criticized party traditionalists opposed to such an alliance as coming "from another age".

Royal also wants to increase the party's appeal by making it cheaper for people to join it and by holding American-style primaries to give supporters a say in selecting its presidential candidate.

Aubry represents the traditional wing of the party and its old pillars, including Fabius and Strauss-Kahn, and is in favour of letting party functionaries and hard-core members choose national candidates.

She also said she was firmly against against any deal with the centrists. But in her successful campaign to become mayor of Lille, she forged a deal with Bayrou's Modem.

Aubry has received the support of the popular mayor of Paris, Bertrand Delanoe, who dropped out of the running for the party leadership during the congress.

Hamon, a long shot, represents the new generation of Socialists and is fiercely anti-Royal. If, as expected, no single candidate wins 50 per cent of the vote on Thursday, he is expected to ask his supporters to vote for Aubry in Friday's run-off election.

But whoever wins the battle, the manner in which it is being fought will likely ensure that someone else will win the war.

According to Pascal Perrineau, head of the Centre for Political Studies, "The big winner is obviously Nicolas Sarkozy. The president doesn't even have to lift a finger. The main opposition party is committing suicide."