Kevin Kuehnert, center, head of the Social Democratic Party’s youth wing, attends an event in Duisburg, Germany, on Feb. 16, during a multicity campaign to persuade SPD members to vote against joining a new government coalition. (Patrik Stollarz/AFP/Getty Images)

After five months of backroom horse-trading and all-night arm twisting, Angela Merkel faces one last obstacle to achieving a stable government in her fourth term as German chancellor.

He’s 28, but he looks younger. On a recent evening, he was unshaven in a black sweatshirt, blue jeans and gray canvas Adidas sneakers. His dirty-blond hair was combed indifferently. He spoke casually, as if talking to friends.

But for two hours, a standing-room-only crowd of 150 in a concrete-block neighborhood of east Berlin strained to hear Kevin Kuehnert’s every word as he unspooled a message of youthful rebellion against plans for four more years of the same centrist-based compromise.

“A grand coalition should be the exception in a democracy. But it’s not the exception any longer,” said Kuehnert, leader of the Social Democratic Party’s youth wing, as he delivered a plea for the party’s rank-and-file members to reject a deal to govern with Merkel’s conservatives. “You reach a point where the commonalities have been exhausted.” 

Young Americans may be sick of hyperpartisan divisions that seem to have left Washington mired in gridlock. But in Germany, teen and 20-something political activists are crying out for an end to the cozy consensus of the Merkel years. They want less dealmaking, more commitment to principles and a sharper distinction between the two establishment parties that have governed Germany throughout its postwar history.

The parties are on the verge of doing so, together, once again — a reprise of the grand coalitions that have defined two of Merkel’s three terms.

Kuehnert, center, joins other SPD figures for a meeting in Recklinghausen on the coalition proposal. The party’s vote on the plan is expected to be close. (Friedemann Vogel/Epa-Efe/Rex/Shutterstock/Friedemann Vogel/Epa-Efe/Rex/Shutterstock)

Yet if Kuehnert and other youth activists succeed in their against-the-odds campaign, the coalition will never come to be. 

Social Democratic (SPD) voters have the chance to weigh in on the agreement between their center-left party’s leaders and the bloc led by Merkel’s Christian Democratic Union (CDU) in balloting that ends Friday. If they reject the deal, Merkel will be left jilted at the altar — and Europe’s most populous nation will be thrust into political turbulence.

The country, where staid politics had become the norm in recent decades, has endured a historically long stretch without a government after elections in September were inconclusive. And Merkel has failed once since then to cobble together a coalition. 

A second failure would leave her with an unappealing choice: lead a minority government that survives from vote to vote in the highly fragmented German Parliament and could collapse at any time, or call new elections. Each would be a first for modern Germany and would call into question just how long Merkel can hang on as chancellor.

Most analysts say it is unlikely that the 464,000 members of Germany’s oldest party will jettison the deal. A recent survey showed two-thirds of the SPD rank and file in favor, and the party’s leadership is campaigning for its passage — albeit with a distinct lack of zeal.

“It’s a matter of two not-so-good alternatives,” said deputy party leader Ralf Stegner. “Going into government is better than early elections and losing even more, compared to an already bad result.” 

The SPD garnered 20 percent of the vote in September, its worst showing since before World War II and just half the level of support it enjoyed two decades ago.

Since the election, the party’s fortunes have declined further: Recent polls show its support falling to about 15 percent, good enough for only third place behind the far-right Alternative for Germany (AfD). The Greens are a close fourth, threatening to displace the SPD as the country’s leading party on the left. Merkel’s conservative bloc has held steady at about a third of the vote. 

Meanwhile, the SPD’s leader of less than a year, Martin Schulz, was forced to resign after embarrassing flip-flops over whether the party would join the government and, if so, whether he would serve in it. 

As the SPD flails, Kuehnert, a student and Berlin native who was unknown politically just weeks ago, has sought to fill the void. In the process, he has set off a battle for control.

“It’s a power struggle between the younger generation and the older generation,” said Juergen Falter, a political science professor at the University of Mainz. 

The party’s youths, Falter said, are enticed by the example of Jeremy Corbyn’s Labour Party in Britain or the Bernie Sanders-led faction of the U.S. Democratic Party — both of which advocate a more resolutely left-wing approach. 

In recent weeks, Kuehnert has traveled across Germany signing up thousands of new members and encouraging them to vote down a coalition that he warns will only betray the SPD’s core beliefs. Instead, he argues, the party needs time in opposition so it can carry out “a radical renewal.” 

The weariness with government-through-consensus is not limited to the young left. Among the more youthful elements of Merkel’s party, too, there is a hunger to ditch the political center after 12 years in which many of the CDU-led government’s signature accomplishments — a minimum wage and legalization of same-sex marriage, for instance — were anathema to conservatives. 

One oft-mentioned candidate to replace Merkel, 37-year-old Jens Spahn, has advocated shifting the party decidedly to the right, particularly on issues such as immigration, to win back voters lost to the AfD.

The leader of the CDU youth wing, meanwhile, publicly lamented the loss of powerful ministries in negotiations with the SPD and suggested that the CDU’s top figures should have fought harder to keep control of key areas such as finance. 

“The mood at the base is more than bad,” Paul Ziemiak said after the coalition deal was announced this month, according to the German weekly Der Spiegel. 

But even as Ziemiak and other young CDU activists have fallen in line behind Merkel in recent days, Kuehnert and the SPD’s youth wing remain in open rebellion.

The depth of their dissatisfaction was on display one recent night in the Marzahn district of east Berlin, a working-class area where the AfD has recently made gains. 

As Kuehnert made his case for a no vote, 19-year-old Lisa-Marie Sager said the appeal resonated with her own fear that her party is more concerned with staying in power than with fighting for principles. 

“Even in a wealthy country like Germany, there are huge gaps between rich and poor and between [pay for] men and women,” she said. “Our leaders will say, ‘We’ve got to do this’ or ‘We’ve got to do that.’ And if the other party disagrees, then the SPD says, ‘Oh, maybe it didn’t matter that much.’ But what’s more important than equality?” 

Sager, a student and local SPD activist, said she was committed to voting down the coalition.

But not everyone was so certain. Even among the party’s young, there was anguish over the SPD’s future as its poll numbers crater — and a fear that the far right will continue to rise no matter how the SPD votes.

“If we have a grand coalition, the AfD will do well. And if we vote no, the AfD will also do well,” said Dennis Kovoussoglou, a 22-year-old biotechnology student. “So what are we going to do?”

Luisa Beck contributed to this report.