German Chancellor Angela Merkel's party has suffered heavy losses in two key regional votes seen as major tests ahead of September's general election.
The centre-right Christian Democrats (CDU) suffered their worst-ever results in Baden-Württemberg and Rhineland-Palatinate, early results showed.
The party has historically enjoyed strong support in these western states.
The poor showing has been widely blamed on public anger at the response to the coronavirus pandemic.
Infections in the country are still high, the vaccination rollout has been sluggish and officials have found it difficult to ease restrictions. Several CDU politicians have also quit over allegations they received huge commissions for arranging government deals to buy face masks.
But the slump has also raised questions about the party's prospects in the national elections later this year.
Mrs Merkel is due to step down as German chancellor in September, after 16 years in office and the setback is the first major test for Armin Laschet, who was elected CDU leader in January.
The 60-year-old centrist, however, is not guaranteed to be the party's candidate for chancellor in the election on 26 September. His rival for the role is Markus Söder, leader of the CDU's Bavarian sister party the CSU.
The party aims to have the matter settled by late May.
What do the preliminary results show?
Germany is a federal state made up of 16 regions. Under this system, there are elections to regional legislatures as well as those to the national parliament, called the Bundestag.
In Baden-Württemberg the Green Party is predicted to hang on to power with about 32% of the vote, with the CDU getting 24%, less than at the previous poll in 2016.
In neighbouring Rhineland-Palatinate, the centre-left Social Democrats (SPD) are projected to retain power with about 35%.
The CDU had led in opinion polls, but it is predicted to get only 27% of the vote.
Both results pave the way for regional alliances between the Greens, the SPD and the liberal Free Democrats. This raises the prospect of a similar coalition forming a federal, or national, government after the general election in September.
Green Party Chairman Robert Habeck said the party would "take this success as a tailwind for the Bundestag election campaign".
Opinion polls show the CDU's national popularity slipping from 40% last June, when Germany was being praised for its initial response to the coronavirus pandemic, to about 33% this month.
Speaking to the BBC, CDU MP Kai Whittaker said the results were disappointing. "It's a bad day for us," he said. "We cannot deny that there's a risk that we're losing touch with the people."
Angela Merkel's CDU did not expect to do this badly. Now, alarm bells are ringing in Berlin.
Party leaders know they are going into September's general election without their greatest asset - Chancellor Merkel herself. Her popularity remains high, but there is increasing dissatisfaction with her government's handling of the pandemic.
The corruption scandal that forced the resignation of three party politicians has not helped. Some fear that the CDU, which just a year ago was predicted to win a comfortable majority and form a coalition - could even be driven from the federal government in the autumn.
It is too soon to make serious predictions about who will be running Germany come the end of the year. After all, voters do not know who the CDU will put forward as their candidate for chancellor.
It will most likely be new party leader Armin Laschet, but the fallout from the regional elections could clear the way for Markus Söder.