Fears over the Japan nuclear crisis triggered a crushing defeat for Chancellor Angela Merkel's conservatives in their German heartland Sunday, as the ecologist Greens roared to a historic triumph.
Merkel's Christian Democrats (CDU) have ruled wealthy Baden-Wuerttemberg, home to industrial giants Daimler and Bosch, for 58 years, but her on-again, off-again support for nuclear power spooked voters ahead of the crucial poll.
The anti-nuclear Greens won a record 24 percent of the vote -- more than 12 points higher than in 2006 -- and were likely for the first time to lead a coalition with the Social Democrats, who garnered about 23 percent.
The opposition edged out Merkel's party and the Free Democrats (FDP), their junior partners in the state and at national level, who claimed a dismal 44 percent between them.
Forty-five percent of voters called nuclear power a key issue in light of the disaster in Japan, and Foreign Minister Guido Westerwelle, the FDP leader, pledged another rethink in Berlin.
"The dreadful events in Japan, the nuclear accident in Fukushima and the consequences for us in Germany: these were the most decisive topics in this state election," Westerwelle said. "It was a referendum on the future of atomic energy."
Social Democrats leader Sigmar Gabriel declared: "Today the final decision on the end of nuclear power in Germany was made."
Green candidate Winfried Kretschmann, 62, who is expected to become the party's first state leader in Germany after campaigning hard on the nuclear issue, claimed a "historic victory".
"It's a dream come true.... We could never have dreamed of a result like this a few days ago," added Franz Untersteller, a Greens spokesman.
The result in the state bordering France and Switzerland marked a debacle for Merkel, 56, after drubbings in North Rhine-Westphalia in May and Hamburg in February.
Calling Japan's emergency a "turning point", Merkel suspended for three months an earlier decision to extend the lifetime of Germany's nuclear reactors, four of which are based in Baden-Wuerttemberg.
She also temporarily shut off the country's seven oldest reactors pending a safety review.
Nuclear power is unpopular in Germany, but polls indicated that voters saw Merkel's zigzagging as an electoral ploy: it cost her support while boosting the Greens.
Adding to the pressure, tens of thousands of Germans hit the streets Saturday in four major cities to protest the government's nuclear policy. Organisers said as many as 250,000 took part.
Meanwhile, in a further triumph for the Greens, strong gains in another election in the western state of Rhineland-Palatinate will force the Social Democrats to cede their absolute majority and join them in a coalition.
The pro-business FDP failed to clear the five-percent hurdle for representation in the state, which will turn up the pressure on the already embattled Westerwelle in a "super" election year with three more polls to come.
Analysts said Merkel's coalition was expected to survive, in large part because the opposition is still too weak at the national level and her party lacks a viable challenger to her.
"The CDU has no one," newsweekly Der Spiegel wrote on its website. "It is chained to Merkel, at least until the next scheduled federal election (in 2013)."
Beyond a stinging blow to morale in Berlin, the loss will make it even harder for Merkel to pass legislation in the Bundesrat upper house and likely prompt fresh calls for her to shore up her rightist credentials.
"The aftershocks of this earthquake will cause confusion in the Berlin coalition," the conservative daily Frankfurter Allgemeine Zeitung wrote, referring to the capital of Baden-Wuerttemberg.
"That will primarily zero in on the ongoing weakness of the FDP, which does not have convincing government personnel, neither in Stuttgart nor at the federal level."