By Lucy White A year ago, the UK’s Green Party was riding high on a surge in the polls sparked by their new populist leader, Zack Polanski. Twelve months later, that bubble has been burst by the governing Labour Party’s own under a new prime minister: Andy Burnham.

The Greens head into their annual conference in their spiritual home of Brighton on Friday with Polanski grappling with how to deal with Burnham, who has steered Labour leftward into Green territory. That makes selling the Green brand harder, especially as Polanski seeks to wrest former Prime Minister Keir Starmer’s old seat of Holborn and St. Pancras from Labour in a parliamentary by-election next week.

“The Greens have been doing well with young voters who are economically disaffected,” said Rob Ford, professor of political science at the University of Manchester. But now, they face a “much more aggressive Labour government” which has returned to its traditional territory of talking positively about public ownership and a more assertive state, he said.

Polanski’s Greens were already stuttering following a string of missteps before Burnham’s ascent to power in July further curbed their appeal. The former Manchester mayor has shown signs of being able to unite the left, with Labour rising 5.4 percentage points since he came to power, and the Greens dipping 3.6 points, according to Bloomberg’s composite poll.

That’s a far cry from a year ago, when the Greens were invigorated by the recent election of Polanski, who had vowed to take on the populist right of Reform UK at their own game. By tapping pro-Palestinian sentiment among Britain’s Muslim and student populations, he siphoned off a swath of Labour voters, winning the Green Party’s first ever by-election earlier this year in Manchester, and quadrupling the party’s seats in a round of local elections in May.

But Burnham has moved Labour leftward, including imposing sanctions on Israeli companies trading in the occupied West Bank, apologizing for the party’s former stance on Gaza and saying it was too slow to recognize Palestine. His conference speech this week veered into policy areas that tend to be popular with the Greens’ target electorate, including pledges to reform the electoral system, explore rejoining the European Union and alter an expensive policy that’s protected rises in the state pension for 15 years.

Polanski is due to give his own speech at 1:30 p.m. on Friday, a pebble’s throw from the shingle beachfront in Brighton — the south coast city which delivered his party its first Green Member of Parliament back in 2010.

The Green leader will announce support for three years of curbs on private rents, in a bid to end the “fear and uncertainty” of renting a home. But a preview of the speech promising to give Britons “breathing space” — echoing Burnham’s slogan — shows how the new prime minister has set the terms of the debate.

Central in his mind will be his own battle to win a seat and join five colleagues in the House of Commons next Thursday. But the competition in Starmer’s former North London stronghold is tougher than Polanski would like. The Green leader’s main competitor is Labour’s Sagal Abdi-Wali, who came to the UK as a refugee from Somalia in the 1990s. While she’s widely seen as the favorite, one Green party official told Bloomberg that canvassing data put the race much closer than some in Labour assume.

Last weekend, the official said, there were indications that undecided voters who’d backed Labour in the 2024 general election were moving toward the Greens.

Nevertheless, Green Party officials are already beginning to prepare the ground for Polanski’s failure, with two pointing out to Bloomberg that Reform leader Nigel Farage had lost seven parliamentary elections before finally securing a Commons seat in 2024.

If he loses, “Polanski’s going to face a real crunch moment with his party in terms of convincing them to stay the course with his approach, at a time where it seems like potentially they’re losing the argument to Labour,” Ford said.

Polanski, who was credited with driving a near-tripling in the Greens’ membership to more than 200,000 people, has faced other hurdles over the last year.

The 43-year-old, who calls himself an eco-populist and has criticized rivals for opacity around their finances, was forced to apologize earlier this year after it emerged he’d failed to pay council tax while living on a houseboat. He was cleared of wrongdoing but his party said he’d “taken steps to pay any council tax he may be found to owe.”Polanski — who is himself Jewish — has also faced criticism for his stance on Israel. He told a hustings in a synagogue last month that Jews “are making ourselves as Jewish people less safe” by failing to criticize Israel for “apartheid and genocide.”

He also faced a backlash after condemning the actions of police when they arrested a suspect in a terror attack targeting Jews in north London.

At this week’s conference he’s come under pressure to distance himself from a motion entitled “Zionism is Racism,” which has raised eyebrows among those in the Jewish community who view Zionism as the necessary struggle for a Jewish homeland. The motion has caused divisions in the party between those longer-standing members who often have more moderate views on Zionism, and recent joiners who are keen to campaign against Israel.

Despite all the recent challenges, the Greens are still polling well above the 6.7% vote share they secured in the 2024 general election. Founded in the 1970s as a party to further environmental policy, the Greens had long been on the fringe of UK politics, but over the past year found themselves in a new era of multiparty politics for Britain, with five parties consistently polling percentages in the double digits.

Burnham may be stemming their advance for now, but Ford said a lot of the policy in Burnham’s speech was dated for some time in the future, with little immediate effect.

“We do have a lot of quite distrustful and impatient voters out there,” Ford said. “My advice to Polanski would be you need to sell your members on the virtues of patience in a volatile political environment.”