Wiesbaden, GERMANY/BERLIN (Reuters) - Germany’s Social Democrats (SPD) elected Andrea Nahles as their first ever female leader on Sunday, hoping she can reinvigorate the country’s oldest party after it suffered heavy losses in September’s election.

Slideshow ( 3 images )

Some 66 percent of SPD delegates at a congress voted for Nahles, a plain-speaking former labor minister and Catholic mother of one who has close links to trade unions and once said she wanted to be either a housewife or the German chancellor.

The 154-year-old SPD, junior partner in Chancellor Angela Merkel’s governing coalition, had to find a new leader to replace Martin Schulz, who resigned after his campaign for September’s election earned the SPD its worst showing since 1933.

Nahles had been widely expected to win but the result on Sunday is second-worst for an SPD party leader in the postwar era, with some members unhappy about the renewed Merkel tie-up that Nahles pushed for likely having voted for her opponent - Simone Lange, the 41-year-old mayor of the northern city of Flensburg.

The SPD remains in the doldrums, with an Emnid poll for newspaper Bild am Sonntag showing its support at 18 percent, lagging Merkel’s conservatives on 33 percent and not far ahead of the far-right Alternative for Germany (AfD) on 13 percent.

Nahles, 47, must now preside over the party’s efforts to revamp itself - coming up with new policies and pushing fresh faces into the foreground - to bring the SPD back from the brink and make it an electoral force to be reckoned with again.

“You can renew a party while it’s in government. I want to prove that from tomorrow,” Nahles said in an impassioned speech before the vote, addressing widespread concerns in the SPD that it would have been easier to reinvent the party in opposition.

Germans are not confident in her abilities - the Emnid poll found less than a quarter believe Nahles can make the SPD successful in her new role - a job that also requires her to try to win back voters the SPD has lost to the AfD.

A former leader of the party’s more radical Jusos youth wing, Nahles was credited with rallying support from a reluctant party for a renewal of the ‘grand coalition’ with Merkel’s conservatives that also governed Germany from 2013 to 2017.

But discord is already growing in the coalition over issues including immigration, euro zone reform and how to handle the diesel emissions crisis. Nahles could pull her party out of the alliance with Merkel if she is unhappy with how it is working and has a prime opportunity to do so in the half-time review after two years when the parties will assess progress made.

It is yet to be seen whether Nahles, with her leftist roots, will seek to shift the party leftwards with an eye to a potential future coalition with the Greens and far-left Linke, or fight Merkel by sticking to the center ground - as the party largely did during the last legislative period.

With her blunt style Nahles is likely to animate political debate and may make Merkel’s life more uncomfortable. She vowed in September to hit the conservatives “squarely in the jaw” after four years in coalition with them. Not having a position in government gives her more freedom to do so.

She must also heal deep divisions within the party which remain over its decision to join once again a coalition with Merkel. Cracks have also emerged in the SPD in recent weeks over its Russia policy and welfare reform, more than a decade after the party spearheaded Germany’s liberalization of the labor market.