Chancellor Angela Merkel's Christian Democrats will lose control of Germany's most prosperous state to the centre-left opposition in a major upset to her centre-right government, according to TV exit polls.
In Baden-Wuerttemberg state, the Greens and Social Democrats (SPD) looked set to win a combined 48.5% in an election on Sunday where Japan's nuclear disaster played a major role. The centre-left has long pushed to end the use of nuclear power.
The Christian Democrats (CDU) and their Free Democrat coalition partners, big backers of prolonging the use of nuclear power in Germany, won a combined 43 percent of the vote, network ARD said shortly after polls closed at 1600 GMT.
The CDU, which has ruled the state for 58 years uninterrupted, took 38 percent and the FDP 5%. The Greens finished second with 25 percent and could lead a government in one of the country's 16 federal states for the first time. The SPD, their likely allies, took 23.5%, ARD said.
In another state election on Sunday in Rhineland-Palatinate, the SPD held onto power with a comfortable victory over the CDU and will likely form a coalition with the Greens.