Defeated Socialist Party presidential hopeful Ségolène Royal will back party favourite Francois Hollande, her former companion, in a primary runoff on Sunday, giving him a small boost against rival Martine Aubry.
Her move came as a second poll showed Mr Hollande, a moderate left-winger, remains in the lead by several points to be picked as the Socialist candidate for the 2012 presidential election.
Ms Royal, who wept after coming fourth in Sunday's first-round primary vote with 7 per cent to Mr Hollande's 39 per cent, said in a statement she would back the man who is father of her four children because he was best placed to win.
"Today I am putting all my support behind Francois Hollande," said Royal, who was the Socialist Party's unsuccessful presidential challenger in 2007. "We must give impetus to the candidate with a clear lead that will not leave the right any foothold."
Mr Hollande replied by statement: "I welcome the elegance and responsibility the woman who was our [presidential] candidate in 2007 and who understands how vital unity is to the strength of an electoral campaign."
Mr Hollande's victory over Ms Aubry, a stauncher leftist who helped bring in France's 35-hour work week, looks less certain since hardline leftist Arnaud Montebourg landed in third place in the first round with a stronger than expected 17 per cent, suggesting strong support for his more radical ideas.
In the first poll of second-round voting plans since then, an Opinionway survey of left-wing voters yesterday showed Mr Hollande's predicted score slipped four points to 54 percent while Ms Aubry's rose four points to 46 percent.
A second survey today by Harris Interactive found 53 per cent of left-wing voters would back Mr Hollande in the second round of the Socialist primary on Sunday against 47 per cent for his rival Ms Aubry, a more old-school leftist.
Mr Hollande and Ms Royal separated in 2007, shortly after Ms Royal lost that year's presidential election to conservative Nicolas Sarkozy, following a 29-year relationship that made them the golden couple of the French left.
Reuters