Socialist challenger Francois Hollande on Sunday led Nicolas Sarkozy in France's first round of voting, setting up a May 6 runoff between the two presidential candidates.

Hollande narrowly led Sarkozy with an estimated 3 percentage points, 28.4% to 25.5%. Marine Le Pen trailed with 20 percent of the vote.

“The people have mobilized in a massive way in the selection and a real level of participation. Eighty percent turnout is a big number. What has been shown is that I'm in the lead. I want to thank you all warmly,” Hollande told supporters on Sunday night.

While Sarkozy remains in the contest, he made history as the nation's first incumbent president to lose at the first hurdle – a psychological blow that will be difficult to rebound from.

A Hollande administration would mean good news for supporters of France becoming the eleventh nation to legalize gay marriage.

France currently recognizes gay and lesbian couples with PACS, a form of domestic partnership. The union offers significantly fewer protections than marriage, and gay couples are barred from joint adoption of children.

Sarkozy has previously pledged to reform PACS into something closer to Britain's civil partnership. However, the law has not changed.

Hollande has said as president he would pursue legislation which would legalize marriage for gay couples.

Last week, Sarkozy reiterated that he is opposed to such unions, saying, “For me, a family is a father and a mother, not two fathers or two mothers.”