PARIS (AP) — Partial results suggest that Manuel Valls, a center-leaning former prime minister who rallied France together after extremist attacks, will confront stalwart Socialist Benoit Hamon in the country's left-wing presidential primary runoff next week.

Hamon, a former government minister, was leading with 35.2 percent followed by Valls with 31.6 percent, based on more than one-third of the vote count, organizers of Sunday's first round of primary voting said.

Whoever wins the Jan. 29 primary runoff will face the April-May presidential election battling more popular candidates from the far right to the far left riding frustration with immigration and economic stagnation.

Tough-talking, center-leaning Valls jumped in the presidential race in December few days after Socialist President Francois Hollande declined to seek re-election —acknowledging his personal unpopularity would lead his Socialist party to defeat in the presidential battle.

Valls, 54, has faced fierce attacks from harder-left rivals who associate him with Hollande's unpopular moves to relax labor protections to encourage hiring.

He argues that he has the experience that France's next leader will need as the country is facing the threat of extremist attacks, and to revitalize a lagging economy.

The Spanish-born politician, naturalized French at the age of 20, is promising to decrease taxes for modest and middle-class households and to boost police and defense.

Hamon, 49, is a lower-profile politician yet he gained popularity by leading a group of rebel Socialist lawmakers who opposed Valls.

A former junior minister and education minister, he left the government in 2014 after he expressed disagreement with Valls' pro-business policies.

He is pledging to push for the introduction of a 750-euro ($800) "universal income" living allowance for all adults in the country.

Hamon is also promising to tax robots, legalize cannabis and repeal labor measures passed by Valls.

The competition promises to be tough for the Socialist nominee in the race for the two-round presidential election on April 23 and May 7.

Polls show more support for conservative candidate Francois Fillon and National Front leader Le Pen.

The left also faces a growing challenge from centrist Emmanuel Macron, 39, a former investment banker who led Hollande's reforms as economy minister, but refused to take part in the Socialist primary.

Far-left leader Jean-Luc Melenchon is drawing voters away from the establishment Socialists, too.

Overshadowing the Socialist voting is the nationalist sentiment that helped fuel Donald Trump's successful campaign for the U.S. presidency and in several countries around Europe.

Le Pen and other European far-right leaders came together Saturday in Germany in a show of strength before multiple European elections this year.