Chancellor Angela Merkel's junior coalition partners gave her conservatives until next year to deliver more policy results, threatening to end their alliance if there is no improvement after both parties suffered in a regional election on Sunday.
Merkel's conservative Christian Democrats (CDU) came home first in the election in the western state of Hesse, but polled just 28 percent of the vote, an exit poll for broadcaster ARD showed. That marked a huge drop from the 38.3 percent the CDU won at the last Hesse election, in 2013.
The center-left Social Democrats (SPD) fared even worse, winning just 20 percent of the vote, down from 30.7 percent and its worst result in the western state since 1946. The party just managed to beat the Greens, who placed third with 19.5 percent.
SPD leader Andrea Nahles said she would use a roadmap with which to measure the progress of the ruling coalition, which has been plagued by infighting, at a mid-term review next year.
"We could then gauge the implementation of this roadmap at the agreed mid-term review, when we would be able to clearly see if this government is the right place for us," Nahles told reporters. "The state of the government is unacceptable."
Her message was clear: the SPD needs to be able to show tangible results to its supporters next year or else the party's leaders will pull out of the coalition with Merkel.
Volker Bouffier, the incumbent CDU state premier in Hesse and a Merkel ally, said his party had achieved its goal of being able to lead the next government in Hesse, but added: "We are in pain because of the losses".
"The message to the parties ruling in Berlin is: People want fewer disputes and more focus on the important issues," he said.
The CDU's poor result in Hesse, after its sister party in the state of Bavaria, the CSU, suffered its worst result there since 1950 two weeks ago, may turbo-charge a debate about who succeeds Merkel and when. She has been chancellor for 13 years.
Merkel's weakness at home may limit her capacity to lead in the European Union at a time when the bloc is dealing with Brexit, a budget crisis in Italy and the prospect of populist parties making gains at European parliament elections next May.