By Paul Carrel
BERLIN (Reuters) - Germany's Greens have proposed holding coalition talks in the city state of Bremen with the Social Democrats and far-left Linke, in a reminder to Chancellor Angela Merkel's conservatives that even if they come first in any elections, they are not guaranteed power.
The Greens' push for a leftist coalition in Bremen is significant because the party, fresh from coming second in May's European Parliament elections, wants federal elections held if Merkel's coalition with the Social Democrats (SPD) collapses.
That scenario has grown more likely after the SPD suffered twin election setbacks in May, prompting their leader to quit.
In the last national parliament, the SPD, Greens and Linke had more seats than Merkel's conservative bloc, although policy divisions - especially on foreign affairs - prevented them from forming a federal government.
While Bremen is a tiny state with a long left-wing history, a so-called Red-Red-Green coalition there would be the first of its kind in Germany's West, demonstrating the Greens' ability to tip coalitions to the left or right as they see fit.
"A Red-Red-Green alliance offers the possibility, with a stable majority, of taking courageous, new steps in the politics of the state of Bremen," the Greens leadership in the northern city state said in a statement late on Wednesday.
A Forschungsgruppe Wahlen poll for ZDF television released on Thursday put support for the Greens at a record 26% nationally, their highest reading in a poll series running back to 1991, and just one point behind Merkel's conservatives.
Together, the Greens, SPD and Linke had 43% support, the poll showed. But with some smaller parties short of the 5% threshold required to win seats in parliament, the alliance would be on the cusp of a majority on the national level.
In Bremen, the Greens' proposal offers the SPD a lifeline to hold on to power after the centre-left party failed to win the most votes there for the first time in 73 years last month, narrowly losing to Merkel's Christian Democratic Union (CDU).
"Coalition building in Bremen is interesting for the implications it could carry for the federal level, especially as the Grand Coalition could well fall apart this year," said Mujtaba Rahman, managing director at consultancy Eurasia Group.
"The automatic assumption of many is that a Green-CDU coalition would be most likely, probably after elections. But Bremen shows that a Red-Red-Green combination might be possible," he added.
Red-Red-Green alliances already hold power in the states of Berlin and Thuringia, in Germany's former Communist East. In Hesse and Baden-Wuerttemberg in the West, the Greens share power with Merkel's conservatives.
The CDU also shed support in the European elections in May. Their leader, Annegret Kramp-Karrenbauer, has been edging the party to the right since she succeeded Merkel as chairwoman in December.
A survey by pollster Forsa released late last month showed most Germans believe Kramp-Karrenbauer is not ready to succeed Merkel as chancellor.
(Reporting by Paul Carrel; Additional reporting by Kerstin Doerr; Editing by Hugh Lawson)