The new leftwing leadership of Germany’s Social Democrats have sounded a cautious note over hastening the breakup of Angela Merkel’s coalition government, dampening speculation that the troubled party could pull the plug on the government as soon as Friday.

In a surprise result, two little-known leftwingers, Norbert Walter-Borjans and Saskia Esken, caused an upset at the weekend when they won the leadership vote of the world’s oldest social democratic party, a move that seemed to signal a rejection of the party’s centrist “third way” phase initiated under the former chancellor Gerhard Schröder.

The result came as a shock not only to the widely expected winner, Germany’s deputy chancellor and finance minister, Olaf Scholz, but also to the victorious pair and their supporters.

The new leaders, both critics of the SPD’s “grand coalition” with Merkel’s centre-right party, had said throughout their leadership campaign that a decision on the future of the governing alliance would be made at this weekend’s party conference in Berlin.

But the latest draft for Friday’s main motion, agreed between Esken, Walter-Borjans, Scholz and the interim leader, Malu Dreyer, seems designed to put the break on a rushed exit by tasking the new leadership merely to “seek a dialogue” with Merkel’s CDU about measures to stabilise Germany’s slowing economy and amend an already agreed climate package.

Profile Norbert Walter-Borjans and Saskia Esken Show Hide Norbert Walter-Borjans The 67-year-old political economist who joined the SPD at the age of 31, has sometimes been referred to as Germany's Bernie Sanders for his insistence that the SPD must lead the country out of the "neoliberal wilderness". He has said the SPD had drifted into believing that lower taxes and VAT rises were the best way to run the country, and he would look to reverse this thinking, in the unlikely event he was elected co-leader. The father of four who paints and sculpts in his spare time, earned a reputation as a risk taker willing to take on the rich and powerful during his time as finance minister in North-Rhine Westphalia, Germany´s most populous state, when he paid €19 million for CDs containing whistleblower's data on thousands of Swiss bank clients. The move prompted tens of thousands to voluntarily pay back €7.2bn in unpaid taxes. In an interview with the Guardian last month, Walter-Borjans - often referred to as NoWaBo for short - said the country was in need of a large amount of investment and that he would rather Germany abandoned its commitment to balancing the federal budget, the so-called "black zero", to free up money for this. "If the economy does indeed enter a downturn then we will need to make massive investments. Because our infrastructure is not in a good state, and nor is our digital infrastructure nor our schools. We have to question the black zero.” Saskia Esken The 58-year-old from Baden-Württemberg is even less well known than her male counterpart. She joined the SPD at the age of 29, and has been in the Bundestag since 2013, taking a clear left-wing position, and like Walter-Borjans also critical of the SPD´s "neoliberal" politics under Gerhard Schröder, and voting against a tightening of the government's extradition policy, but has largely remained low-profile. Married with three children, she counts among her hobbies woodland walks with her dog, as well as music and literature. During the campaign as well as criticising the grand coalition, she made a particular point of stressing the need for reform of the European Union including introducing a Union-wide fiscal policy including cracking down on tax evasion. Photograph: Axel Schmidt/AFP

In a move designed to mend relations between leftwing and centrist factions in the SPD, the Guardian understands the wording of the motion could lead to Scholz and other ministers being invited to join the talks.

Kevin Kühnert, the hoodie-wearing leader of the SPD youth wing, who is seen as one of the architects of Esken and Walter-Borjan’s shock victory, has also appeared to cool on the prospect of an exit from the grand coalition, known as “GroKo”.

“If you leave a coalition, you end up giving up a degree of control,” Kühnert told the Rheinische Post newspaper in an interview. “SPD delegates should bear that in mind too when they made up their mind.”

“If need be, I am not afraid to go into an election with the SPD in the next three months,” said Kühnert, who is in the running to be voted deputy leader at the weekend. But many party insiders question whether the leftwingers calling the shots have the right staff and action-ready strategy to go into fresh elections early next year.

Another reason why even seasoned GroKo critics are reluctant to bring down the current government is that it has yet to implement one the SPD’s totemic projects, a raising of the basic pension for low-income workers employed all their lives.

Yet the risk of a chaotic end to Merkel’s fourth term in office remains. Apart from formally voting in Esken and Walter-Borjans as new leaders, delegates could propose and pass a motion to ditch the government’s commitment to balanced budgets, the so-called schwarze Null (“black zero”).

A strongly worded motion committing SPD ministers to further spending could push the more fiscally conservative finance minister Scholz to throw in the towel, unravelling Merkel’s current cabinet.

Walter-Borjans told the Guardian in an interview last month that driving Germany to commit to more spending would be a defining issue of his leadership.

“If the economy does indeed enter a downturn then we will need to make massive investments. Because our infrastructure is not in a good state, and nor is our digital infrastructure nor our schools. We have to question the black zero,” said Walter-Borjans, a former finance minister of the state of North-Rhine Westphalia.

“If that doesn’t work with our coalition partner then that’s not a good sign.”