The German opposition Social Democrats (SPD) have inflicted a heavy defeat on Chancellor Angela Merkel in a regional election in the port city of Hamburg.
The SPD won 48.3% of the vote in Sunday's election, giving them 62 seats in the 121-seat state assembly.
Mrs Merkel's Christian Democrats (CDU) plunged to 22%, so they will lose three seats in the upper house (Bundesrat).
Mrs Merkel blamed the blow on local issues, but she faces six more German state elections this year.
The centre-right CDU is in danger of losing power in the big southwestern state of Baden-Wuerttemberg in March.
"About 80 per cent of the issues that played a role in Hamburg were local Hamburg matters," Mrs Merkel said on Monday, but she admitted it was "a bitter defeat for the CDU".
The SPD's Olaf Scholz, a former labour minister, will become the new mayor of Hamburg, enjoying an absolute majority in the state assembly.
The CDU lost 22 percentage points in the election - one of its worst ever regional results.
The Greens triggered the election by quitting a coalition with the CDU in Hamburg in November. They took 11% of the vote.
BBC Berlin correspondent Stephen Evans says the slump in CDU fortunes indicates a rough road to the federal elections in 2013 - and it might also make it harder for Mrs Merkel to keep her ruling coalition together before then.
He says there are local factors behind the result, but the CDU may also be suffering a backlash from the recession. The economy is now growing fast, but only after a steep decline.