KEY POINTS:
The struggle to become the Next Big Thing on the French left wing has exploded into open warfare after the defeated presidential candidate Segolene Royal announced a bid to become the First Secretary, or leader, of the Socialist Party.
This week Paris Mayor Bertrand Delanoe, who is likely to be her main rival, will publish a book called De l'Audace! (Courage!), setting out his political philosophy and ambitions.
With six months to go before the Socialists choose their new leader, the pair have, in effect, joined battle for the right to be both the party chief and the candidate-elect for the presidential elections in 2012.
Royal, 54, has been bounced into an early declaration by the rising popularity of the gruff, moderate, competent mayor. Although his open homosexuality is regarded as a serious handicap by some political analysts, Delanoe, 57, is running far ahead of Royal in recent national opinion polls.
Royal made it clear at the weekend that she would be a candidate to succeed her former partner, Francois Hollande, as First Secretary.
"If the party members agree with the ideas we put before them ... if they consider it useful ... then I will accept with joy and determination this wonderful mission."
Her announcement drew immediate fire from the supporters of other potential candidates, including Delanoe. They accused her of trying to turn the struggle for the soul of France's main opposition party into one of personalities rather than ideas.
Dominique Strauss-Kahn, a former Finance Minister, who heads the International Monetary Fund in Washington, also let it be known he regarded himself as the best centre-left candidate to challenge the unpopular President Nicolas Sarkozy in 2012.
Several other party figures, including the Mayor of Lille, Martine Aubry, and the former Europe Minister Pierre Moscovici, are also likely to challenge for the leadership in November.
The party leader is not necessarily guaranteed to be the presidential candidate in 2012. But both Royal and Delanoe covet the post as a way of shaping the party around their own ideas and ambitions.
Royal blames her presidential election defeat partly on her own mistakes and partly on the failure of a much-divided party to support its candidate.
Both she and Delanoe come from the moderate, reformist wing of the party but they differ on how to adjust Socialist ideals to the modern world.
Royal wants to pursue the mixture of grassroots participation politics and appeals to traditional values on which she fought the 2007 election.
Delanoe is more in the pragmatic, managerial tradition of his mentor, former Prime Minister Lionel Jospin.
The first challenge facing any new Socialist leader will be to prevent the party from collapsing into moderate and idealist, or revolutionary wings.
Draft amendments in the party's declared aims, to be discussed in November, would abandon all references to revolutionary change and accept the primacy of managed market economics - already practised but never the accepted theory.
SEGOLENE ROYAL
* Beaten by Nicolas Sarkozy in last year's presidential election.
Won the Socialist nomination for the presidency after having to endure sniping from male politicians within her own party.
* Was blamed for a presidential campaign that was seen as lacklustre and gaffe-strewn.
* Her former partner, Francois Hollande, is the current First Secretary of the party.
BERTRAND DELANOE
* Has been the Mayor of Paris since 2001.
* Was re-elected ithis year with 57.7 per cent of the vote for a new six-year-term.
* Virtually unknown before the 2001 election.
* Has gained notoriety for organising new and unusual events in Paris, such as the "Paris Beach" where sand is dumped on the banks of the River Seine every summer.
* Is openly gay.
- INDEPENDENT
