BERLIN, March 24 (Reuters) - Seven of Germany's 16 states are holding elections this year, making 2011 a crucial test for Chancellor Angela Merkel's ruling centre-right coalition of Christian Democrats (CDU) and Free Democrats (FDP).
Merkel's CDU already lost control of Hamburg to the centre-left Social Democrats in the first state vote on Feb. 20 and could be defeated in another vote on Sunday in Baden-Wuerttemberg. The next federal election is set for 2013.
Following are details of the state elections.
March 27 - BADEN-WUERTTEMBERG
The wealthy southwestern state is a traditional CDU bastion but is shaping up as a major test for Merkel. Losing the state, an economic powerhouse, could leave Merkel vulnerable to attack within her party, analysts say.
Having ruled the state since 1953, the CDU has angered voters by pushing ahead with the construction of a railway station in Stuttgart despite a wave of at times violent protests .
The CDU has also been hurt by the nuclear disaster in Japan and Merkel's decision to abruptly shut down, at least temporarily, seven of Germany's 17 nuclear plants after she had pressed for extending the lives of nuclear power in Germany.
A recent poll put the CDU, led in the state by premier Stefan Mappus, at 38 percent, with the FDP at 5 percent. The SPD and Greens have a 5 point lead with each polling 24 percent. Losing the state would be a heavy setback for Merkel.
March 27 - RHINELAND-PALATINATE
Kurt Beck of the SPD has been premier of the rural western state for 17 years and has ruled with an absolute majority over the past five years. Polls show he should be able to retain power -- with the surging Greens as a coalition partner.
The CDU has put forward Julia Kloeckner, 38. Also warranting attention is the FDP if they make it into the state assembly; they are now polling 5 percent, just enough to clear the hurdle.
May 22 - BREMEN
The city-state has had SPD mayors since 1945 and that is unlikely to change. Jens Boehrnsen is likely to win the race.
The SPD, polling around 34 percent, has governed in a coalition with the Greens, at 20 percent, the past five years.
Sept. 4 - MECKLENBURG-VORPOMMERN
Erwin Sellering of the SPD took over his predecessor's grand coalition with the CDU in 2008 after the latter resigned.
In recent polls, the SPD leads the CDU by 3 points. The Left -- currently at 15 percent -- could tip the balance if the SPD gets the most votes and opts for a coalition with them rather than another grand coalition with the CDU.
Sept. 18 - BERLIN
The Greens stand a strong chance of winning one of the country's top political posts, with Renate Kuenast, a minister in Germany's last SPD-Greens government, challenging incumbent Mayor Klaus Wowereit of the SPD.
The SPD are just ahead of the Greens in polls. An SPD-Greens coalition or an SPD-Left coalition are possible.
Following are details of the first two 2011 state elections:
February 20 - HAMBURG
The CDU was swept from power in Hamburg with their worst result since World War Two, plunging 20.7 percentage points from the last election to 21.9 percent.
Losing Hamburg and its three seats in the Bundesrat, or upper house, left Merkel's coalition four votes short in the 69-seat chamber, making it far more difficult to try to get legislation through without concessions to opposition demands.
March 20 - SAXONY-ANHALT
The CDU fell 3.7 points to 32.5 percent in the poor eastern state of Saxony-Anhalt but will likely be able to remain in power in a grand coalition with the SPD, who won 21.5 percent. The FDP won only 3.8 percent of the vote and were ejected from the state assembly in Magdeburg, which party chief Guido Westerwelle, the foreign minister, called a "bitter defeat". (Compiled by Annika Breidthardt and Erik Kirschbaum; editing by Alison Williams)