Last week saw the publication of the list of candidates running in the upcoming by-election in Holborn and St Pancras, following the resignation of Sir Keir Starmer. The former Prime Minister had represented the seat since 2015 but announced his intention to step down on 1 September. The contest, due to be held on 8 October, will see the Green Party leader, Zack Polanski, look to join his five MPs on the Commons benches.
Polanski has had an unconventional route into frontline politics. He worked as an actor, school activity provider and hypnotherapist before entering politics, joining the Liberal Democrats in 2015 and switching to the Greens in 2017. He was elected to the London Assembly in 2021 and became the Greens’ deputy leader from 2022 to 2025, before standing as a single candidate for the party leadership in 2025 against the joint ticket of Adrian Ramsay and Ellie Chowns. He won by a landslide in September 2025.
Since taking charge, Polanski has overseen a period of rapid growth for the Greens. Under his leadership the party won the 2026 Gorton and Denton by-election, after which membership passed 220,000 – a threefold increase since he became leader – and he led the Greens to their best-ever results in the 2026 local elections. He has also branded his politics as “eco-populist” and hosts his own podcast, the first by a British party leader.
However, his personal ratings and party unity have taken a knock more recently, with the Greens dogged by accusations of antisemitism and Polanski himself criticised over a series of gaffes, questions over his tax affairs, and an “inflated CV”. Within his own party, there are ongoing tensions between those wanting the party to adopt a more hardline policy towards Israel, and those seeking a more cautious approach. Polanski has so far not commented on the motion scheduled to go before the party’s upcoming conference, with some members commenting to the press that his attempts to be all things to all people will shortly run into difficulty.
The challenges facing the party can be seen most clearly in recent opinion poll ratings. In March-April this year, the Greens reached 20% in some polls, averaging in the mid-to-high teens. However, since then there has been a steady decline, with recent polls putting the party around 10%. This has coincided with the ‘Burnham bounce’ that has seen a resurgence in support for Labour.
Even setting that infighting aside, the challenge in Holborn and St Pancras remains a significant one. The seat has been held by Labour continuously since its creation in 1983, with majorities ranging from a relatively marginal 13.9% in 2005 to a landslide 51.7% in 2017. Turning a seat with that history Green would be a remarkable feat – but if any Green candidate has the profile to attempt it, Westminster-watchers suggest it is Polanski. Furthermore, Labour will be determined to hold the seat – the first by-election the party has contested since Burnham became Labour leader.