(CNN)Six hundred delegates from Germany's Social Democratic Party (SPD) will descend on the city of Bonn this Sunday for a special party congress.
All eyes are on one agenda item: A vote on starting official coalition negotiations with Chancellor Angela Merkel's Christian Democrats (CDU) and their more conservative sister party, the Christian Social Union (CSU).
Just six weeks ago, the SPD voted overwhelmingly to start the initial exploratory talks. This time, it looks to be on a knife edge.
But if the vote passes, the collective sigh of relief is likely to drown out any celebrations.
It's nearly four months since Germany's federal election, in which support for the country's two largest parties slumped leaving Merkel with a mathematical and ideological quandary in her effort to form a new government.
Talks with the liberal FDP (Free Democratic Party) and Green Party collapsed, leaving a renewal of the so-called "GroKo" (Grosse Koalition or Grand Coalition) as the only option -- unless Merkel opts to rule alone in a minority government or put the country on the path to new elections.
"No one is particularly excited about another grand coalition," said Christoph Nguyen, political scientist at Free University Berlin. "But most of the alternatives are even less pleasant to consider."
"It's a bad option, but probably the least bad option."