The frontrunner in the race to lead France's Socialist Party against President Nicolas Sarkozy in next year's presidential vote has gained the support of his ex-lover and 2007 presidential candidate, Segolene Royal.

Her endorsement of Francois Hollande, the father of her children, came Wednesday just hours before a crucial and final primary debate against rival Martine Aubry in the battle for the Socialist party nomination.

Hollande, who currently leads Aubry in the polls by six to eight percent, took first place in last week's first round of the Socialist primary with 39-percent. Aubry was second with 31-percent, while hardline leftist Arnaud Montebourg took third place with a surprising 17-percent. Royal, who lost to President Nicolas Sarkozy in 2007, took fourth place and was eliminated with just seven percent.

The debate is expected to feature questions on the economic crisis, social issues and foreign affairs that will be posed by a panel of journalists.

The closeness of the polls could leave third-place finisher Montebourg as the deciding factor in the primary runoff for the nomination. He says he will wait until after watching the debate to decide which candidate to endorse.