* Chancellor Merkel's party beaten for 6th time in 2011
* Social Democrat mayor Wowereit wins third term
* FDP crashes out of Berlin assembly with 2 percent
(Updates with quotes, reactions and details)
By Erik Kirschbaum and Stephen Brown
BERLIN, Sept 18 Germany's Social Democrats beat
Angela Merkel's conservatives in a regional vote in Berlin on
Sunday, handing the chancellor her sixth election defeat this
year ahead of a key euro zone vote in parliament in two weeks'
Merkel's centre-right coalition suffered a further setback
when their junior coalition partners at the national level, the
Free Democrats (FDP), failed to clear the five percent threshold
needed to win seats -- for the fifth time this year.
The beleaguered FDP, which had attempted to attract voters
in Berlin with its increasingly euro-sceptic tactics, plunged to
2 percent from 7.6 percent in 2006, exit polls showed.
Their eroding support nationwide could destabilise Merkel's
centre-right coalition, analysts said.
Merkel, under fire for her hesitant leadership in the euro
zone crisis, is halfway through a four-year term. But election
setbacks for her CDU have hurt her standing before the vote on
euro zone measures in parliament on Sept. 29.
"We would be wise to show humility about this result," said
a visibly stunned FDP deputy party leader, Christian Lindner.
"It's a low-point but also a wake up call. We knew it was going
to be a difficult year and that's been dramatically confirmed."
The SPD won 29.5 percent of the vote in Berlin, down from
30.8 percent in 2006 in Germany's largest city with 3.4 million
inhabitants, according to an exit poll on ARD television.
SPD Mayor Klaus Wowereit appeared to be headed for a third
five-year term, with the Greens as his most likely coalition
"The best part of the result tonight is that the voters
showed the FDP they won't get anywhere with populist attacks
against Europe," said SPD leader Sigmar Gabriel, celebrating his
centre-left party's sixth win in seven regional votes this year.
"It shows the voters are smarter than the FDP campaign
strategists and that you can't win an election by campaigning
against Europe. The FDP tried that and failed."
EUROSCEPTIC MESSAGE FAILS
The CDU won 23.5 percent, up slightly from 21.3 percent in
2006 but well below the 40 percent the party used to win in
Berlin in the 1980s and 1990s. The Greens won 18 percent, up
from 13.1 percent in 2006, and the Left party fell to 11.5
percent from 13.4 percent.
The SPD and Greens have pledged support for boosting the
euro zone bailout fund for countries like Greece in a crucial
vote in parliament vote on Sept. 29, when Merkel may face a
revolt from more eurosceptic members of her coalition.
Greens leader Cem Oezdemir said the FDP had "tried to turn
this election into an anti-European plebiscite" after its party
leader, Economy Minister Philipp Roesler, said it should not be
taboo to debate an "orderly" Greek debt default.
"Losing the election with 2 percent is a dramatic setback
for the FDP and I hope they draw the right lessons," Oezdemir
said. "Anti-European populism has no support in Europe and in
Germany, thank goodness, and that's good news for our country."
The Pirate Party, running on a campaign for reform of
copyright and better privacy in the Internet age, came out of
nowhere to win a stunning 8.5 percent.
The SPD, in opposition at the national level since 2009,
hopes their re-election in Berlin will help build up momentum to
oust Merkel in the next federal election in 2013 -- or possibly
sooner, if her government were to collapse.
"We're not the successors to the FDP," said Gabriel, when
asked if the SPD would be ready to replace the FDP if the
government were to fail before 2013.
The SPD has ousted or helped defeat the CDU in Hamburg and
Baden-Wuerttemberg this year and remained in power elsewhere.
The CDU has lost six of seven regional votes this year,
holding onto power only in the eastern state of Saxony-Anhalt.
The fresh loss in Berlin will add to Merkel's woes before a
Bundestag vote on Sept. 29 to give the European Financial
Stability Fund (EFSF) more powers.
Merkel did not make any comments on the Berlin election. But
senior CDU lieutenants tried to put a positive spin on the
result, noting that it was slightly improved from 2006.
Peter Altmaier, conservative parliamentary floor leader,
said the CDU's gains had helped prevent a renewal of the
SPD-Left coalition that has ruled in Berlin under Wowereit for
the last 10 years.
"This is solid backing ... for Angela Merkel's policies,"
Altmaier said, adding that Merkel has spoken out unambiguously
in favour of euro zone rescue measures.
"Merkel has made it very clear in recent weeks that the CDU
stands by its pro European profile and vocation," Altmaier said.
"We link stability with European consciousness and that has been
honoured by the voters. Some euro sceptic posters were put up in
Berlin at the last moment but they had no impact."
(Reporting by Erik Kirschbaum, Stephen Brown, Alexandra Hudson
and Natalia Drozdiak)