By Michelle Martin
BERLIN (Reuters) - Leading German Social Democrats (SPD) urged delegates on Tuesday to back coalition talks with Chancellor Angela Merkel's conservatives and warned that shunning another tie-up would further damage the party's already dire ratings.
SPD members will vote on Sunday on whether to back full-blown coalition talks with the conservatives. Last week they agreed to a coalition blueprint but some in the party have bashed, saying it does not bear sufficient hallmarks of their party and that they would be better off in opposition.
The SPD leadership has unanimously agreed to recommend they be given a mandate to pursue coalition talks.
SPD General Secretary Lars Klingbeil told Die Zeit newspaper's online edition that he understood the widespread scepticism in his party about agreeing to a re-run of the 'grand coalition' that governed Germany in the last four years, but warned against the alternative.
"Before voting at the party congress SPD delegates should be aware that there are only two realistic scenarios: negotiating further or new elections," he said.
The SPD had planned to reinvent itself in opposition after a poor election showing in September but was persuaded to enter coalition talks with the conservatives when Merkel's attempt to form a coalition with two smaller parties failed in November.
The latest INSA poll showed the SPD slipping to 18.5 percent, its worst ever result in that particular survey, and weaker still than the 20.5 percent it fetched in September's election - which was its poorest post-war performance.
Merkel needs the SPD to back the alliance if she is to shore up a fourth term after 12 years at the helm. Refusal by SPD delegates to hold further talks could lead to new elections or a minority Merkel-led government for the first time in the post-war era.
Edgar Franke, a spokesman for the SPD's conservative "Seeheimer Kreis" wing, said if his party refused to join a grand coalition, it risked sliding to 15 or 16 percent in a new election.
"And it won't recover from that in the long term," Franke told Focus magazine.
The most divisive issues for the two blocs concern taxes, pensions, migration and healthcare but both parties are aware that a grand coalition is one of the last options on the table.
The coalition question has split the SPD, with branches in Berlin and the eastern state of Saxony-Anhalt recommending their members vote against, and Brandenburg and Hamburg in favor of coalition talks.
Those against also argue that such an arrangement would allow the far-right Alternative for Germany (AfD) to become the largest opposition party.
Nevertheless there is a consensus at the top of the party that it should enter formal coalition talks, and this received a boost on Wednesday when a dozen SPD mayors from big cities called on delegates to vote in favor.
"We should not reject the opportunity to form Social Democratic policies for people, which is contingent upon participating in government," the mayors in a joint statement.
SPD leader Martin Schulz has gone on a charm offensive in the biggest state of North Rhine-Westphalia (NRW) to get its backing for talks but Norbert Roemer, head of the SPD's parliamentary group there, said results of the exploratory talks did not make clear enough that there would be a fresh start.
He told the Sueddeutsche Zeitung: "In our party - and this is true of me too - there's a lot of mistrust of Ms Merkel and her troops."
Paul Ziemiak, head of the conservatives' youth wing, urged the SPD to agree to a grand coalition, telling Tagesspiegel newspaper the SPD needed to stop talking about itself and adding: "Our country is at stake."
(Reporting by Michelle Martin; Additional reporting by Holger Hansen; Editing by Raissa Kasolowsky)