Germany's centre-left opposition won a wafer-thin victory over Chancellor Angela Merkel's coalition in a major state election on Sunday.
The Social Democrats (SPD) and Greens won a single-seat majority in Lower Saxony's parliament, ousting the coalition of Ms Merkel's conservative Christian Democratic Union (CDU) and the pro-market Free Democrats that has run the region for 10 years.
Ms Merkel will seek another four-year term in a national parliamentary election expected in September.
The outcome could boost what has so far been a sputtering campaign by her SPD challenger Peer Steinbrueck.
"This evening gives us real tailwind for the national election," Green spokeswoman Katrin Goering-Eckardt claimed. "We can and will manage to replace the centre-right coalition."
The CDU and Free Democrats have now lost four states since the smaller party joined the coalition government in 2009.
The alliance has a poor reputation at the national level, with the Free Democrats taking the blame for frequent infighting.
Ms Merkel's CDU has meanwhile been bolstered by a relatively robust economy, low unemployment and her hard-nosed handling of Europe's debt crisis.
The SPD party improved a little on its feeble performance five years ago in Lower Saxony, polling 32.6 per cent.
The Greens gained more, winning 13.7 per cent.
That gave them 49 and 20 seats respectively.
The Left Party won just 3 per cent of the vote, down from 7 per cent in 2008. As it missed the 5 per cent threshold the party has lost all of its 11 seats.