The SPD will today decide whether to start formal coalition talks with Angela Merkel’s conservatives, a move which would bring Europe’s economic powerhouse one step closer to a stable government.
Leader Martin Schulz is facing a strong backlash from the party’s left and youth wings, which argue that the SPD should reinvent itself in opposition.
The party recently scored its worst election result in September since Germany became a federal republic in 1949.
Around 600 delegates, meeting in Bonn, will debate and vote on whether their leaders should push ahead with coalition talks on renewing an alliance with Merkel’s conservatives that took office in 2013.
The two blocs, which both bled support to the far right in the September 24 election, struck a preliminary deal last week but critics, including the party’s youth wing leader Kevin Kuehnert, say the agreed blueprint does not bear enough of the SPD’s hallmarks.
Sunday’s vote will also be watched closely abroad as Germany has Europe’s largest economy and Merkel has long played a leading role in the continent’s economic and security affairs.
Senior Social Democrats have cited progress in efforts to win support for formal talks after the SPD’s biggest regional branch in North Rhine-estphalia (NRW) recommended its members vote in favour of entering negotiations.
But the support comes on the condition that Schulz pushes for more concessions on labour, health and migration policies.
Mr Schulz defended the preliminary deal despite calls for more concessions on labour, health and migration policies.
He tweeted: “Toll-free day care facilities for children, a strong Europe and decent care of the elderly – that will only happen when we join the government.
“To seize the opportunity to considerably help many people is a duty for me.”
SPD parliamentary leader Andrea Nahles said she expected formal talks to happen.
“Nevertheless, I ask everyone in my party to take responsibility: Please consider the consequences if this government option fails,” she told Welt am Sonntag.
A negative vote by the SPD would prolong political deadlock at a time when Germany’s humming economy is producing record budget surpluses.
French President Emmanuel Macron is counting on Berlin to join forces and overhaul the European Union in the light of Britain’s decision to leave the bloc.
Possible scenarios in case of a rejection by the SPD would include new elections or a minority government for what would be the first time in Germany’s post-war era.
But an optimistic Mrs Merkel, who has been in power since 2005, said: “We will wait for the SPD party congress and then hopefully start coalition talks.”