HERNE, Germany (Reuters) - Just a few years ago, Germany's Social Democrats were pinning their hopes on Hannelore Kraft as their answer to Angela Merkel. Now Kraft is struggling just to stay on as a regional leader and hopes of her party unseating the chancellor are fading fast.
Kraft, whose name means "strength" in German, is fighting to hold onto power in the state of North Rhine-Westphalia (NRW), which votes on Sunday in a poll that will serve as a barometer of popular opinion before the Sept. 24 national election.
After suffering humiliating defeats in two other state votes this year, the Social Democratic Party (SPD) may have to retain NRW if its new national leader - Martin Schulz - is to mount a serious challenge to Merkel's bid for a fourth term at the helm of Europe's most populous country and pivotal economy.
Elections in NRW, home to around a third of Germany's blue chip companies but also the rust-belt Ruhr region, have historically influenced federal politics. In 2005, a crushing defeat for then-Chancellor Gerhard Schroeder's SPD prompted him to call an early election that he lost to Merkel.
With more than a fifth of Germany's overall population, the state is now governed by a left-leaning alliance of the SPD and Greens. But an ebbing of support for the environmental party means that coalition is likely to break up.
What's more, some polls have shown the SPD, which has been the dominant party in NRW for 45 of the last 50 years, neck-and-neck with Merkel's conservatives, who are hoping to build on their recent victories in the smaller states of Saarland and Schleswig-Holstein to land a third win on Sunday.
"This election will give Mrs Merkel and her conservatives a tailwind if they do well, or strengthen her challenger Martin Schulz if the SPD get a good result, so it will have a significant impact either way," said Ulrich von Alemann, a political scientist at Duesseldorf's Heinrich Heine University.
Kraft, a popular former handball player with a common touch, is doing what she does best: hitting the campaign trail and mixing with voters in a punishing schedule that is taking her across the western state of 18 million people.
Speaking before boarding her blue campaign bus, Kraft lamented the SPD's loss on Sunday in Schleswig-Holstein in the far north, but said her campaign in NRW was going well.
"Now we must fight harder than ever before in North Rhine-Westphalia," Kraft, who has repeatedly said she sees her future in NRW rather than on the national stage, told reporters.
"I said we'd do it around the clock and we will - you can see everyone's motivated here," she said during a stop on her 11-hour "battle bus" tour that took in four towns.
The NRW election is also a crucial hurdle for Schulz, who revived the SPD early this year but has since seen support slip. A poll on Tuesday showed the SPD at its lowest national level in more than three months at 27 percent.
An NRW election poll published on Tuesday showed the SPD on 33 percent, Merkel's Christian Democrats on 30 percent, the pro-business Free Democrats (FDP) on 13 percent, the Greens 7 percent and the far-left Linke 5 percent – the threshold for entering parliament.
The SPD finds itself in this tight race even though Kraft, a tram driver's daughter, enjoys more personal popularity than her conservative challenger Armin Laschet, a former journalist and son of a mining foreman.
Kraft, 55, has considerable personal appeal - those who attended a breakfast rally in the former mining city of Herne praised her as "down-to-earth" - but must contend with NRW's policy problems including high crime rates and creaking infrastructure.
Public safety concerns have also risen since mass sexual assaults in Cologne on New Year's Eve 2015.
And over the last decade, poverty has increased more sharply here than in any of Germany's 15 other states.
NRW has a large Turkish community that has voted SPD in the past. Now, widespread fears for security and social harmony due to an influx of migrants since 2015 are likely to help the anti-immigrant Alternative for Germany (AfD) enter its 13th state assembly on Sunday. The AfD was at 7 percent in Tuesday's poll.
Merkel, scenting blood as her conservatives pull away from the SPD in national polls, has campaigned in NRW and accused Kraft of not ruling out a coalition with the Greens and the far-left Linke - a prospect that unnerves centrist voters.
Kraft stressed at a rally in a vast hall in the city of Bochum she thought the Linke was "neither willing nor capable of governing". The chances of such an alliance have dimmed with both the Linke and Greens hovering just above 5 percent.
Editing by Paul Carrel and Mark Heinrich