Doris Vollmer is clearly new to politics. She fumbles her power points, and blanks on a fellow candidate’s name. But the German physicist also captures her audience’s attention as she pokes a glass of water balanced on the podium. Imagine, she says, this is rising global temperatures.

“It’s going up! It’s rising,” she shouts. Water splashes across the stage as the glass falls. “You can’t put the water back into the glass. You can’t reverse a tipping point . . . Politicians want to follow the old strategy: negotiate, negotiate. But you can’t negotiate with nature.”

It was an unusual stump speech by one of Germany’s newest national parties — the Klimaliste, or “climate list”. Party chair Vollmer and her peers, scientists and activists wearing jeans and Birkenstocks, may seem easy to write off.

But they represent the double-edged sword that Germany’s growing climate activism could become for the ascendant Green party in September’s federal elections.

Doris Vollmer

Even as Green party leader Annalena Baerbock makes a credible bid to replace Angela Merkel as chancellor, the party once derided as a chaotic cohort of hippies and idealists is under attack from the opposite flank: for being too establishment.

“There needs to be a new type of party. A party that listens to the science. That involves people. That acknowledges the global challenge,” says Alicia Sophia Hinon, a Berlin candidate for the Klimaliste.

It is not a critique usually lobbed at the Greens. But under the stewardship of Baerbock and her co-leader, Robert Habeck, a party long gridlocked between its leftwing “fundis” and centrist “realos” has become a streamlined political force, determined to attract Germany’s change-wary, conservative centre.

Most of the grassroots have followed, begrudgingly. But some have rebelled, worried that the Greens have softened their climate goals and, should they form the next coalition government — most likely with Merkel’s Christian Democrats (CDU) — they might compromise further.

“The Greens are thinking in terms of power politics,” says Alexander Grevel, a Klimaliste campaigner in Stuttgart. “We are here to put pressure on the Greens to do more for the climate again.”

The Klimaliste’s goals are less a divergence from Green policies than an intensification. Whereas the Greens seek carbon neutrality within 20 years, the Klimaliste want it “as fast as possible,” at most in 10 years. The Greens want a carbon tax of 60 euros per tonne; the Klimaliste say it should be 195 euros.

Political analysts such as Andrea Römmele, at Berlin’s Hertie School, say the Green party is still on track to join government, but warns striking too many compromises would strengthen Klimaliste and other campaigners, creating a long-term political challenge for the party.

“If they give in a lot, especially towards business,” she said, “then there is more room on the left side of the party spectrum.”

The voters the Klimaliste claims to represent may not be a large electoral force, but they are influential. The student-led Fridays for Future and Extinction Rebellion protests vaulted climate policy to the forefront of the national agenda, forcing politicians to react.

They helped boost Germany’s Greens to their best-ever results in the 2019 European parliament and even won a recent case to toughen climate law in the constitutional court. In March, Klimaliste candidates in regional elections in Baden-Württemberg, the only state run by the Greens, pushed the party to recommit to limiting global warming to 1.5 degrees.

Both sides agree such pressure is useful.

“I’m happy to have people who keep us sharp,” says Reinhard Bütikofer, a European Parliament member for Germany’s Greens. “It helps highlight the big issues.”

Robert Habeck and Annalena Baerbock, co-leaders of the German Greens

The Klimaliste, around for only about a year, will field just 70 candidates through Germany’s direct voting list. If they win at least three seats, they can create a parliamentary group to join inquiries and legislative committees.

Baden-Württemberg’s elections, however, suggest even a small presence can hurt green causes politically. The Greens were one seat away from clinching a coalition with the centre-left Social Democrats and clearing a path for stronger climate policies, but instead had to form a government with the CDU. Some Greens blamed the Klimaliste.

“Some of us were crying,” one Green politician admitted privately. “In three counties, we lost votes to them . . . Strategically, it’s really stupid [of them] to do this right now.”

Grevel is unapologetic. Since the Greens won this regional leadership a decade ago, he argued, they have not only short-changed their renewable energy goals, they are lagging behind some CDU-led regions.

The Greens counter that Baden-Württemberg, heartland of Germany’s auto industry, was a bigger challenge and a more conservative state to reform.

“A programme that never gets you close to governing can be as radical as you want, but it won’t achieve anything,” Bütikofer said.

None of this worried the Greens a few months ago, as they soared to the top of polls after Baerbock’s nomination. Now they have dropped 10 points behind the CDU — hit by reports over mistakes in her CV, allegations of book plagiarism, and mudslinging campaigns.

At a Berlin Fridays for Future protest — a weekly happening until the election — few openly support the Greens. “We are not here as a support vehicle for the Greens,” shouts one university student, wrapped in an earth flag at a “Dance Demo,” where socially distanced dancers writhe to techno beats. “We are about climate justice.”

Hinon wants to use this momentum to shake up all German leaders, Green or not: “We want to bring the street into the parliament.”