Germany’s embattled coalition parties were holding separate crisis talks on Monday after the resignation of the leader of the centre-left SPD plunged the government into turmoil.
Andrea Nahles said she was stepping down following her party’s poor performance in the European elections.
Her resignation has raised concerns that Chancellor Angela Merkel’s coalition government could collapse.
Mrs Merkel said she respected her “far-reaching” decision.
Rolf Mutzenich, deputy chairman of the SPD, put himself forward to serve as the party’s interim leader after an initial meeting on Sunday.
Ms Nahles’ long-term replacement is yet to be determined, leaving the coalition hanging in the balance while further talks take place.
The 48-year-old’s centre-left party came third, behind Mrs Merkel’s Christian Democrats (CDU) and the Greens, in the elections.
The disappointing result has caused disquiet in the party, whose left-wing members have criticised Ms Nahles for remaining in the coalition.
Ms Nahles became SPD leader in April 2018, replacing Martin Schulz who had also resigned following the party’s poor performance in elections. She had been expected to run for the position again and her resignation took analysts by surprise.
The coalition between the CDU and the SPD is due to last until federal elections in 2021, but correspondents say Ms Nahles’s resignation could lead to the SPD leaving, triggering a snap poll.
How will the talks unfold?
Parties in Ms Merkel’s fragile government are set to hold separate crisis talks about the fate of the coalition on Monday.
A first round of talks was held by the SDP’s leadership on Sunday, but the question of who would succeed Ms Nahles was not resolved.
Several senior party figures, including Vice-Chancellor Olaf Scholz and Lower Saxony’s Prime Minister, Stephan Weil, have ruled themselves out.
Former SDP leader Thomas Oppermann said it could take “one, two months” to choose Ms Nahles’ replacement.
He said the political instability was “not a good overall situation” and warned his party against “waiting for further defeats”, alluding to the forthcoming elections in three East German states in September and October.
Polls suggest the SDP may suffer losses in those elections. In the Forsa survey, the SPD dropped by five percentage points to 12%, its lowest-ever score on a national level.
No obvious choice
Analysis by BBC Berlin Correspondent Damien McGuinness
Many never wanted the SPD to be in government again in the first place.
Party left-wingers blame plummeting support on years of messy compromise with Angela Merkel’s conservatives.
Now pressure is growing on the SPD to quit the coalition and bring down the government, in the hope that fresh elections would help them ditch the conservatives and build a left-wing coalition.
The problem is new elections are unlikely to help. Current polls place the SPD in third place after the Greens. There is no leader-apparent ready to take over. And the party’s message on many big issues, from climate change to migration, remains unclear.
In 2017 it took six months of wrangling to form this government. That was followed by half a year of internal bickering that exasperated voters.
The only parties that would benefit from more struggles for power within Germany’s two big parties would be the Greens and the right-wing populist AfD.
What did Andrea Nahles say?
Ms Nahles said she would stand down as party leader on Monday and as head of its parliamentary group on Tuesday.
In a statement by the SPD on Sunday she said: “The discussions within the parliamentary faction and feedback from within the party have shown me that I no longer have the necessary support to carry out my duties.”
She had earlier announced that the leadership contest would take place on Tuesday.
Where does this leave the coalition?
If the SPD were to leave the coalition, the fall of the government would be likely to trigger fresh elections.
But the left wing of the SPD has been urging the party to pull out since it entered government last year. They say that compromising with conservatives has been costing them support.
Mr Scholz told the Tagesspiegel newspaper he had ruled out entering another such coalition.
“Three grand coalitions in a row would not do democracy in Germany any good,” he said in the interview before Ms Nahles announced her resignation.
On Sunday, Mrs Merkel’s successor as CDU leader, Annegret Kramp-Karrenbauer, warned the SPD not to endanger the coalition.
“I assume the SPD will undergo a succession in short order without hindrance to the functioning of the grand coalition,” she said.
“In the CDU we believe that this is not the time to play politics. We want to serve our country with good governing policies.”
The latest crisis come days after Mrs Merkel dismissed reports of a rift with Mrs Kramp-Karrenbauer.
Two unidentified officials quoted in a Bloomberg article had said Mrs Merkel believed her successor was not up to the job. But the German chancellor dismissed the claims as nonsense.