Chancellor Martin Schulz

:: One in five German voters headed to the polls in a key state election Sunday.

About 13.1 million eligible voters in North Rhine-Westphalia casted ballots to elect a new regional Parliament for the sprawling industrial region, which has a large migrant population and has been a Social Democratic Party (SPD) stronghold for decades.

But surveys ahead of the vote showed the center-left party running neck-and-neck with Chancellor Angela Merkel’s Christian Democratic Union (CDU), with some even placing the party ahead.

The SPD had been ailing nationwide but saw a surge in support in February when Schulz took over. But that support failed to translate into votes in the last two state elections, when the CDU won comfortably. Schulz shrugged off the two disappointments.

“Sometimes you lose, sometimes you win,” he told voters at a rally in Leverkusen on Thursday.

An election in Germany’s biggest state is always significant, but it carried higher stakes this year, being the last regional vote before national polls.

CDU’s candidate Armin Laschet casted his vote in Aachen.

In the run-up to Sunday’s vote, Schulz had held more than 30 rallies in the state, where he began his political career in his hometown of Wuerselen.

The party banked its hopes on incumbent State Premier Hannelore Kraft, 55, who secured 39.1 percent in a 2012 vote, while the CDU clinched just over 26 percent.

Merkel had been pounding the streets in the state of 18 million people, including 4.2 million of migrant origin.

In the town of Haltern am See on Wednesday, she took aim at Schulz’s arguments, saying the CDU offers “justice in the sense of jobs, strong budgets, funds for local communities.”

She also urged voters to look at her government’s economic record — with 7.5 percent unemployment, the state fares worse than the national rate of 5.8 percent, she said.

Merkel had also blamed the incumbents for persistent traffic jams that “are longer than from here to the moon.”

The CDU had also accused the state’s SPD-Green governing coalition of security failures.

State Interior Minister Ralf Jaeger has faced criticism for failing to detain Anis Amri, the Tunisian asylum seeker suspected in the deadly Berlin Christmas market rampage last year.

Amri had lived in the state and was deemed a threat by intelligence officials, but Jaeger argued that there was insufficient evidence to lock him up.

On Jaeger’s watch, Cologne also became the scene of mass sexual assaults by groups of mostly North African men on New Year’s Eve of 2015-2016, inflaming the debate over the 890,000 asylum seekers Germany welcomed in 2015.

The populist AfD (Alternative for Germany), which has railed against the migration influx, hoped to win its first seats in North Rhine-Westphalia.