PARIS (AP) — French left-wing voters cast ballots Sunday in a nationwide presidential primary aimed at producing a Socialist candidate strong enough to confront formidable conservative and nationalist rivals in the April-May general election.

That's no easy task. France's once-powerful left is struggling for political survival after President Francois Hollande's pro-business reforms split his Socialist Party. And in a campaign marked by anti-immigrant populism and fears of economic stagnation, many disillusioned working class voters are abandoning the left for far-right leader Marine Le Pen.

Tough-talking, center-leaning former Prime Minister Manuel Valls is a leading contender in Sunday's first round primary, but has faced fierce attacks from harder-left rivals who associate him with Hollande's unpopular moves to relax labor protections to encourage hiring.

Valls is promising to decrease taxes for modest and middle-class households and to boost police and defense. 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.

Arnaud Montebourg, a former economy minister who left Hollande's government amid feuding over economic policies, has pledged "France first" economic policies and wants to require CEOs to raise employees' wages if they raise their own.

Casting his ballot Sunday in central France, Montebourg said he hopes to "bring together the other components of the left wing and win this presidential election."

Another disenchanted former government minister, Benoit Hamon, is promising to tax robots, legalize cannabis and give 750 euros ($800) in "universal income" to all French adults.

Paris voter Francoise Danzon said he struggled to choose.

"I think Montebourg's and Hamon's programs are really on the left side, and they are interesting, but I don't really believe in it totally. Because to me it doesn't seem really realistic," Danzon said.

The other candidates are Vincent Peillon, Francois de Rugy, Sylvia Pinel and Jean-Luc Bennahmias. Hollande declined to seek re-election.

The top two vote-getters in Sunday's primary advance to a runoff set for Jan. 29. For the winner, a bigger challenge comes after that, in the race for the two-round presidential election 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 ahead of multiple European elections this year.

All French citizens are allowed to vote in Sunday's primary if they pay 1 euro ($1.04) and sign a document saying they share the values of the left.

As a sign of leftist voters' disaffection toward the Socialists, the turnout is on track to be much lower than in the conservative primary last November.

Socialist Party organizers said that more than 1 million people had voted by 5 p.m. — out of the more than 40 million French citizens registered on electoral rolls. More than 4.3 million people voted to choose the conservative nominee, Francois Fillon.

___

Nadine Achoui-Lesage and Catherine Gaschka contributed to this report.