Support for Germany's Social Democrats falls to two-year low - poll

BERLIN (Reuters) - Germany's opposition Social Democrats (SPD) fell to a two-year low in an opinion poll out on Wednesday while the gap in support for its struggling candidate Peer Steinbrueck and popular Chancellor Angela Merkel widened five months before an election.

The SPD tried to rally morale at a party congress in Bavaria on Sunday, despite evidence from polls that its best hope of regaining power is to form a "grand coalition" under Merkel. Steinbrueck served as finance minister during her first term from 2005-2009.

Support for the SPD is at 22 per cent, according to the latest survey by Forsa, carried out before the congress. That is lower than their 2009 election result of 23 percent, which was the worst post-war performance by the 150-year-old party.

Forsa, which tends to mark the centre-left party lower than other pollsters and put it on 23 percent last week, said the new poll showed SPD support at its lowest since mid-2011.

The survey for Stern magazine and broadcaster RTL suggested Merkel's centre-right coalition would be able to form a new governing majority after the election on September 22, with 47 percent support versus 45 percent for the combined opposition.

The SPD's buoyant Greens allies advanced a point to 15 percent. Both the SPD and Greens rule out teaming up with the hardline Left, who were on 8 percent.

In line with other recent polls, 58 percent of respondents said they would choose Merkel as leader while only 17 percent preferred Steinbrueck. It was a gain of 1 point for Merkel and a two-point loss for Steinbrueck, a moderate forced to adopt a left-leaning platform.

Merkel's conservatives rose a point to 42 percent and their Free Democrat (FDP) allies just passed the 5 percent threshold for entering the Bundestag lower house. Support for the FDP has tumbled since the party's record high result in the 2009 vote.

(Reporting by Stephen Brown; Editing by Pravin Char)