Why Zack Polanski has gambled on Holborn and St Pancras

Keir Starmer’s resignation as an MP, delivered mere hours before his successor first appeared at the despatch box as prime minister, sets up the sixth by-election of 2026 and the seventh of this parliament. 

The coming contest in Holborn and St Pancras follows a series of by-elections of varying significance, including Nigel Farage’s recent brush with self-styled “intergalactic space warrior” and satirical candidate Count Binface. The stakes were undoubtedly higher in Makerfield, which returned Andy Burnham to parliament after years in the relative wilderness. Burnham’s Makerfield victory set in train the sequence of events that led to Starmer’s twin resignations – first as prime minister, then as an MP – and therefore this latest by-election.

Future chroniclers of Starmer’s downfall will also consider the February 2026 contest in Gorton and Denton. Here, the decision by the Labour National Executive Committee (NEC) to block Burnham’s candidacy provided a crucial boost to the Green campaign. Hannah Spencer was elected as the MP for Gorton and Denton, becoming her party’s first parliamentarian to represent a constituency in the north of England. The Green rout in Gorton and Denton set the scene for the May 2026 elections and the Labour leadership crisis that followed.

Taken together, recent by-election results – from Runcorn and Helsby in May 2025 (Reform gain) to Makerfield and Clacton – form a pretty complete narrative of the development of British politics. At the same time, the signals sent by these contests have proved strikingly consistent. Voters used each by-election as a means of registering dissatisfaction with the status quo.

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The lessons of recent contests remain after Starmer’s resignation, but the landscape has changed. Burnham’s succession has translated into polling gains for Labour; Politico’s poll-of-polls metric has Labour tied with Reform UK, while a series of recent surveys have placed the party in the lead. 

This “Burnham bounce” is now set for its first real test in Holborn and St Pancras – provided by Zack Polanski.

Starmer’s resignation immediately prompted speculation that Polanski could stand to succeed him. The Green leader chose not to contest Gorton and Denton, instead signalling an interest in standing in a future London seat should one become available. Starmer’s resignation created that opening, and so Polanski has confirmed his intentions. Speaking to the Camden New Journal, Polanski said he was “excited by the prospect of representing this place in parliament.” Only local members stand between the Green leader and his party’s candidacy in Holborn and St Pancras.

Polanski’s declaration changes the shape of the race.

Firstly, his candidacy will ensure a more competitive contest. In Makerfield, we saw how Burnham’s status and strategy transformed the campaign, dispelling initial concerns that the constituency was prime Reform territory.

Labour’s victory in Holborn and St Pancras in 2024 was comfortable but complicated. Andrew Feinstein, the activist and former member of the South African National Assembly, ran in the then-Labour leader’s constituency on a pro-Palestine, anti-austerity platform, placing second with 7,312 votes (18.9%). The Green Party candidate, David Stansell, came third on 4,030 votes (10.4%). Overall, Starmer dropped 17 points on his 2019 result. These totals point to the existence of a meaningful base of support in the constituency to the left of Labour, which could be energised by a high-stakes campaign fronted by Polanski.

Holborn and St Pancras will be the third by-election in a row contested by a leader of a national party or a de facto leadership candidate. Polanski’s status – leader of the Greens since September 2025 – will ensure stronger cut-through and motivate his supporters. His challenge is to construct a progressive coalition in the constituency, consolidating the left-of-Labour vote. 

Polanski’s prominence also strengthens the Green pitch. His central message will be that, while voters may like Burnham or at least prefer him to Starmer, his election would maintain pressure on the government to pursue a progressive agenda. According to this framing, the choice in Holborn and St Pancras is not simply Green versus Labour, or even Polanski versus Burnham – but between placing a prominent progressive voice in parliament or increasing Labour’s substantial majority by one. 

Labour will plan to continue the momentum of the Makerfield insurgency. The campaign could point to Burnham’s progressive pedigree and even the criticisms he made of Starmer during his long leadership campaign. Labour will want to secure an endorsement for Burnham’s approach to government, treating the campaign as a de facto vote of confidence. 

The Holborn and St Pancras by-election will ultimately be shaped by the tension between Labour’s strengthened national position under Burnham and Polanski’s capacity to consolidate and mobilise the constituency’s progressive base.

Above all, Polanski’s challenge means that the outcome will be of immense national significance, whichever party prevails.

For the Green leader, the contest offers a chance to arrest his party’s recent decline and atone for his own missteps. For the prime minister – whose path to power was shaped by the rise of a credible challenger on Starmer’s left – it presents an opportunity to seize on recent polling gains and inflict a significant setback on the Greens, triggering deeper disillusionment within their ranks. 

Victory for Labour would also represent a second by-election triumph for Burnham since June: one in a Reform-facing constituency and the other in Green target territory.

A significant loss for Polanski would surely weaken his hold on the Green Party and risk exposing internal tensions. It would undoubtedly reinforce the prevailing narrative that his standing has waned in recent months, and further complicate claims that the Greens are a genuine rival to Labour’s historic dominance of progressive politics.

But the greatest risk for Polanski would have been not standing at all. That decision would have been treated as unequivocal evidence of both his and his party’s relative decline in recent months.

In Holborn and St Pancras, Polanski has placed himself at the centre of British politics again. He stands ready to reap the rewards or suffer the consequences.