On paper, Holborn and St Pancras should be one of the last places Labour needs to worry about.
It has been Labour since 1983, with Keir Starmer winning almost half the vote in 2024. Yet his decision to stand down has turned his former constituency into one of the most intriguing by-elections in Britain this year.
So, does Zack Polanski actually have a chance?
Yes — but he has a mountain to climb.
The market saw it coming
Labour opened around 2/7 and quickly shortened to around 1/5, while the Greens were initially available at 10/3.
Then Polanski entered the picture.
Green odds have since shortened to below 2/1 with some firms, while Labour have drifted back towards 2/5. The market clearly sees Polanski’s candidacy as a boost to the Greens’ chances.
We previously highlighted the value in backing the Greens at 10/3, anticipating Polanski entering the race. They have now shortened enough for our liking.
In our previous blog, we also highlighted the value in 3/1 on Polanski to be the next major party leader to go. His decision to target Starmer’s old seat gives that earlier call an interesting new dimension.
Why did Starmer quit?
The official explanation was that Starmer wanted to move on from Parliament and pursue work outside the Commons.
The timing, however, has inevitably invited speculation.
His resignation came just as Andy Burnham became prime minister, handing his successor an immediate political headache in the constituency Starmer had represented for more than a decade.
There has also been speculation that leaving Parliament would free Starmer from the ongoing obligations surrounding MPs’ outside earnings.
A seat that once embodied Starmer’s dominance of Labour’s metropolitan base has suddenly become a test of whether Burnham’s popularity can extend beyond the North.
This isn't quite the progressive fortress people think
The historical case for Labour is formidable.
But Holborn and St Pancras is not quite the progressive activist fortress it is sometimes portrayed as.
It is arguably more “West London” than “East London”: socially liberal, highly educated and affluent in parts, but with plenty of incrementalist-left and established Liberal Democrat voters alongside the more radical progressive activist base.
The Conservatives have also historically managed respectable vote shares here.
The 2005 election is particularly instructive. Labour fell to 43.2%, while the Liberal Democrats surged to 29.3%, gaining more than 11 points. The Conservatives also secured almost 19% of the vote.
That Lib Dem surge came during the Iraq War era and demonstrated that voters here are capable of moving dramatically when presented with a compelling alternative.
That is the precedent Polanski is trying to exploit.
The May elections provide a useful reality check
Even at what was arguably Labour’s nadir under Starmer, Labour remained more than ten points ahead of the Greens across the constituency.
That makes a Green victory far from inevitable.
But the direction of travel matters.
The Greens have gone from being a peripheral force to a serious presence in Camden, while Labour’s support has become considerably more vulnerable than it was when Starmer first won the seat.
The question is whether that vulnerability survives the change of prime minister.
Burnham has changed the equation
This is Polanski’s biggest problem.
The Greens’ argument under Starmer was relatively straightforward: Labour had alienated traditional left-wing voters, while the Greens offered a more convincing progressive alternative.
But Starmer is gone.
Andy Burnham is enjoying a honeymoon. YouGov’s polling put him at +12% favourability, making him the most popular new prime minister since Theresa May at that stage.
Ipsos’ latest figures are even more striking, with 40% viewing Burnham favourably compared with just 19% for Polanski.
Polanski’s own ratings have also deteriorated. YouGov recorded more than 50% viewing him unfavourably, up 16 points from the local elections.
The Green pitch is therefore no longer:
“Unpopular Labour versus the progressive alternative.”
It is potentially:
“Popular Burnham versus Zack Polanski.”
That is a much harder election to win.
The left-wing arithmetic is moving too
This is where the wider political picture becomes important.
Earlier in the year, Labour represented only just over 40% of the wider left-wing bloc, while Reform represented more than 60% of the right-wing bloc.
Under Burnham, Labour’s share of the left-wing bloc has risen to around 54%, while Reform is closer to 50% of the right-wing bloc.
That matters in Holborn.
A fragmented right is largely irrelevant to the outcome here. What matters is whether voters who broadly sit on the left see Labour as the most effective vehicle for defeating the right, or whether they see this by-election as a rare opportunity to elect a Green MP.
Burnham’s popularity makes the first option considerably more attractive.
For Labour, this is an opportunity to contain the Green challenge on the left and establish itself as the clear anti-Reform option.
The left-wing and muslim protest vote is also split
The news of Andrew Feinstein not standing was originally music to Polanski's ears.
That could have been the single most important difference from 2024.
Feinstein won 18.9% as an independent in the general election, while the Greens took another 10.4%.
Now that Feinstein is out, the progressive vote has a much clearer route towards one candidate.
Or so we thought...
In steps our old friend George Galloway. The former Labour MP, kicked out by Blair for opposing the war in Iraq, has spent the past two decades seeking revenge on his old party.
And by-elections are just his speciality... As a young Labour MP, Galloway dismantled the SDP leader Joy Jenkins from his seat. In more recent years, 'Gorgeous George' has been able to utilise geopolitical issues in the Middle East to turn out the vote in seats with a large muslim population. In 2005, he took Bethnal Green, in 2012 Bradford West, and most recently in 2024 he took Rochdale - all gains from Labour.
On this occasion, however, he will be a thorn in the side of Polanski's Greens who are both essentially eating from the same dinner plate. Galloway himself has aimed his early attacks on the Green leader, claiming he is just another member of the establishment who is wrong both on his support of Ukraine, and trans issues.
Whilst Galloway may not win on this occasion, he knows how to turn out the muslim vote, and that may just be enough to split the Green vote and give Labour a clear path to retaining this seat. The Worker's Party opened at 200/1 but quickly shortened to 150/1. We will believe that is still quite a big price for a seasonal master of the by-election dark arts. We expect that price to come down some more as campaigning begins.
The Greens have been preparing for this
This isn’t Polanski parachuting into completely unfamiliar territory.
The Greens have targeted Holborn and St Pancras for years. Former Green leader Natalie Bennett stood here, and the party has steadily built a local organisation.
The May elections demonstrated how far that organisation has come.
Polanski’s candidacy therefore combines two things the Greens previously lacked: a serious local base and a nationally recognised party leader.
The fact that the Greens believe the seat is winnable is significant.
They would not be putting their leader into the contest if the only realistic objective was a respectable second place.
The betting picture
As we mentioned previously, we highlighted the value in backing the Greens at 10/3 ahead of the Polanski announcement.
They are now around 15/8, and we think they’re short enough.
Labour, meanwhile, have drifted back out to around 2/5.
We actually think 2/5 represents a decent price for Labour to hold the seat. It could make for an interesting addition to some roll-ups, with Labour still looking well placed to retain what should be a fairly comfortable hold.