By Erik Kirschbaum
BERLIN (Reuters) - Germany's defeated Social Democrats may struggle to rally support for a 'grand coalition' with Angela Merkel's conservatives from activists who fear the party could wither further in the shadow of the popular chancellor.
The SPD suffered its second-worst post-war performance at weekend polls that confirmed Merkel's domination of the political stage. Its leaders meet under chairman Sigmar Gabriel on Friday to decide how best to salvage party fortunes.
The deliberations amount to a "Zerreissprobe" (breaking test) for the SPD and for Gabriel. Joining a grand coalition under Merkel is seen by some as a "lose-lose" proposition for Germany's oldest political party.
"The SPD had an extremely poor result and there are a lot of people in the party who'd rather stay in opposition," said Thomas Jaeger, political scientist at Cologne University. "They fear the party's identity will be lost in a grand coalition."
The SPD chairman, already under pressure over the party's drubbing, has himself been blamed for picking the wrong candidate for chancellor - a centrist for a left-leaning campaign strategy - and the wrong policy focus: raising taxes.
But the man with a booming voice and sharp tongue, still in command of Germany's second biggest party, will be pivotal in deciding whether to accept being Merkel's junior partner again.
For some, the fate of Merkel's allies in her last coalition, the Free Democrats, is a salutary lesson. The party had lost so much support since creation of the government in 2009 that it failed to win a seat for first time since 1949.
Nearly two-thirds of Germans want the SPD to join Merkel's conservatives in a 'grand coalition' government. But many in the SPD don't want to get run into the ground as unappreciated and unrewarded partners in an alliance with the woman known to detractors as the 'Black Widow' of German politics.
Gabriel, 54, has sat on the fence in his public comments since Sunday's election left the SPD with just 25.7 percent of the vote, their second worst post-war performance after the 23-percent debacle in 2009 which followed four years with Merkel.
"The SPD is not waiting in line after Frau Merkel ruined her previous coalition partner," Gabriel said on Sunday evening.
A day later, he already sounded less opposed to the idea of repeating the right-left alliance of 2005-2009, saying the SPD would be prepared to listen to what Merkel had to offer.
"The result is open," he said.
Gabriel is the man to watch on Friday and in weeks to come. A former high school teacher, who spoke for the first time this year of his strained relationship with his father, a committed Nazi, Gabriel has stabilized the SPD since taking over in 2009.
He raised eyebrows by opting not to run for chancellor and persuading former finance minister Peer Steinbrueck to stand instead. Gabriel said he wanted to spend time with his newborn daughter, but the talk was that he knew Merkel, who went on to garner 41.5 per cent of the vote, was unbeatable.
SPD insiders think Gabriel secretly relishes the opportunity of leading the party into a grand coalition because he would be vice chancellor as well as either foreign, finance or labor minister, providing a big stage to match his ego.
Many in the SPD want nothing to do with a grand coalition and are wary of Gabriel. Usually a man in a hurry, he is being uncharacteristically cautious.
Those on the left are demanding that all card-carrying party members - more than 472,000 - be allowed to vote on any decision to join a grand coalition, an unwieldy, unpredictable process.
"It's possible the party's grassroots would reject a grand coalition in such a vote and that would force Gabriel and other leaders to resign," said Juergen Falter, political scientist at Mainz University. "Party members need to be persuaded and he needs time for that. That way he can put pressure on the CDU."
A total of 200 regional and national leaders will meet at 6 p.m. (12 noon ET) on Friday to discuss the SPD's options. They may recommend agreeing to exploratory talks.
The SPD's hesitance means talks could drag. In 2005, it took two months to agree the terms of the last grand coalition.
"There's no reason to step on the gas and make decisions that won't be acceptable," said former foreign minister Frank-Walter Steinmeier, the SPD's leader in parliament.
Many Social Democrats fear their party could fall below 20 percent by the 2017 election - a loss of half of the 40.9 percent they won in their last big victory in 1998, under Gerhard Schroeder.
They also worry that the radical Left party, which would be the largest opposition party in parliament, would poach left-leaning voters from the SPD.
"Ninety percent of SPD members in my region are against a grand coalition," said Hannelore Kraft, the powerful premier of the largest state, North Rhine-Westphalia - the SPD's heartland.
Kraft, an early frontrunner to be the SPD candidate for chancellor in 2017, would have a better chance if the party remained in opposition. She and Hamburg mayor Olaf Scholz are seen as dangerous opponents to Gabriel in the SPD leadership.
More pragmatic SPD leaders say it is their responsibility to help form a stable government and recall the succinct words of Gabriel's predecessor Franz Muentefering, architect of the 2005 grand coalition. "Opposition is crap," Muentefering said.
(Additional reporting by Holger Hansen; Editing by Stephen Brown and Ralph Boulton)