Chancellor Angela Merkel dealt a devastating blow to her main rival today, four months before national elections, when early results showed her party securing a strong win in a regional vote in Germany's biggest state.
Her Christian Democratic Union (CDU) clinched 34.3 percent of the vote in North Rhine-Westphalia, first results showed, snatching control of the sprawling industrial region which has been a Social Democratic Party (SPD) stronghold for decades.
The SPD only managed to garner 30.6 per cent, sharply down from its 2012 score of 39.1 per cent, in a serious hit to confidence ahead of general elections in September.
SPD deputy chief Ralf Stegner called it a "very dark day for the SPD" but said the game is not over.
"The boxer SPD has received a serious punch but is still standing," he said.
With a fifth of Germans -- 13.1 million -- eligible to vote in North Rhine-Westphalia, an election in the western state is always closely watched.
It carries even higher stakes this year, being the last regional vote before national polls and having a direct impact on whether the SPD can close a nationwide gap of around 10 percentage points with the CDU.
"We are going into the national elections with a lot of confidence," said lawmaker Michael Grosse-Broemer, who heads the CDU parliamentary group in the Bundestag, noting that the latest win gave the party an extra boost.
But the results marked a huge blow to Martin Schulz, who had generated a strong surge in support for the SPD when he took over the party in February.
Schulz himself had acknowledged the importance of today's vote after casting his ballot in his hometown of Wuerselen.
"The result today is above all one of the regional elections in North Rhine-Westphalia. But it's a vote that will have an influence, there is no question about that," he said.
The SPD had already suffered two setbacks since Schulz took over, with the CDU scoring strong victories in the small states of Saarland and Schleswig-Holstein.
But the NRW setback may raise serious questions on the centre-left party's strategy.
Schulz, who held more than 30 rallies in the state, had hoped that his push for "social justice" would resonate in NRW, which has lagged behind western Germany economically.
He argued that many people are struggling in temporary or low-paid jobs even though the country as a whole is growing richer.
But Merkel, who had also gone all out to sway the state of 18 million people, including 4.2 million of migrant origin, took aim at Schulz's arguments.