PBC By-Election Bumper
Voters in Gorton and Denton head to the polls on Thursday in a by-election that will be watched far beyond the boundaries of the constituency. Since the market opened, we have highlighted what we believed to be the key value opportunities. Now, on the eve of polling day, it is worth taking one final look. With several additional markets introduced this week, the betting landscape has expanded significantly, creating fresh opportunities for those looking to take a position on the outcome. This contest is no longer being viewed as a routine by-election. Market moves, shifting sentiment, and increased liquidity suggest growing interest from both political observers and bettors alike. The addition of new markets — including turnout and party performance lines — has opened up further angles beyond simply backing the outright winner. As polling day approaches, volatility is likely to increase, and late swings in price could present further value. Whether you are backing the favourite, looking for an outsider, or trading short-term movement, this by-election now offers more depth and opportunity than at any previous point in the campaign.
Winner (Outright)
We highlighted the value early on when the Greens were available at 6/1, as we felt the firms had underestimated Burnham’s blocking and the shift in local dynamics. Since then, the market has moved dramatically. The Greens have shortened to as low as 1/3, reflecting strong momentum and heavy backing. However, once they went odds-on, we felt the price became too short and that they were worth taking on. Both Reform and Labour were available at prices as big as 5/2 for either to win the by-election. Even now, we believe around 6/4 represents value, particularly against an odds-on favourite in what remains a volatile contest. Our stronger preference is Reform. The split on the left creates real uncertainty, with many voters on the ground seemingly unsure who the natural tactical option is to keep Reform out. That confusion could ultimately work in Reform’s favour. Meanwhile, Advance UK appears to have gained little traction during the campaign, and that lack of momentum may further boost Reform’s chances. With turnout and vote-splitting key factors, this race still looks far more competitive than the headline odds on the Greens suggest.
Conservatives to lose their deposit (Under 5%) (NAP)
The Conservatives were already reduced to a rump in Gorton and Denton in 2024, managing just 7.9% of the vote. Yet it’s entirely plausible that they haven’t hit rock bottom. Since 2024, the party’s national polling has continued to deteriorate, at times averaging only in the mid-teens. At the same time, Reform has clearly consolidated its position as the dominant force on the right. Unlike in 2024, Reform now stands to benefit from tactical voting among right-leaning voters who see them as the most viable vehicle to challenge Labour. The Greens’ rise — and particularly the profile of their candidate in this by-election — may also influence voting behaviour. Some traditionally Conservative voters could lend support elsewhere to block what they perceive as a more radical left candidate. In this scenario, right-wing voters drift to Reform, while more centrist, moderate Conservatives tactically back Labour, as seen in the more affluent, traditionally Tory parts of Runcorn and Helsby. Whichever way you cut it, the Conservative vote appears set to fragment further. Against that backdrop, odds of 5/4 on the Tories losing a further 3% of their vote share look attractive given the current political dynamics.
Voter Turnout (Next Best)
Turnout at the 2024 general election was surprisingly low. Only 47% of the Gorton and Denton electorate voted, which raised many eyebrows. However, this is understandable: most of the constituency’s Brexit and 2019 Boris Johnson supporters stayed home, while a strong Labour majority was considered inevitable both locally and nationally. The constituency also has a large student and ethnic minority population—demographics that traditionally exhibit lower turnout rates. By-election turnout is typically around two-thirds of the previous general election turnout. In this case, that would suggest a turnout of roughly 31–32%. However, the special circumstances of this by-election could push turnout higher. Recent council by-elections, as well as last year’s local elections, show that Reform is successfully mobilizing first-time voters and long-time non-voters. A similar effect could occur in Denton. This, in turn, could trigger a wider surge on both sides: more students and ethnic minority voters may turn out to prevent a Reform candidate from winning. A comparable example is the 2020 US presidential election, where turnout reached record levels due to the polarizing figure of Donald Trump. Could the by-election outperform the general election? Unlikely. Records show that a British by-election exceeding its previous general election turnout has not occurred since the 19th century. Given all this, 35–40% and 40–45% at Evens seem like the most sensible play.
Reform Over 29% Vote Share (Next Best)
This has been one of the most difficult by-elections to predict in recent memory, made particularly tricky by the fact that it’s a three-way race. Both Labour and the Greens are competing for the left-wing/anti-Reform tactical vote. Unlike the Caerphilly by-election, Labour genuinely believes it can win this seat and has invested significant time and resources into the campaign. The Prime Minister’s visit to the constituency is a strong signal that the party is feeling confident. With neither Labour nor the Greens establishing themselves as the clear front-runner on the left, predicting their vote share is extremely challenging. Both parties could finish anywhere between first and third, with a wide range of possible outcomes. Reform, by contrast, has a more predictable base. Their vote share has a relatively narrow range, with most support coming from the white working-class Denton. Farage’s party is consistently expected to capture around a third of the vote. On the right, there appears to be little vote splitting. Both the Conservatives and Advance UK have been virtually absent during the campaign and across the media. Almost all polling around the by-election has put Reform above 29% of the vote, and I believe the betting lines have been generous. A vote share above 29% for Reform seems highly likely.
To Finish 2nd (Value angle)
Looking at the prices for the three main parties in this market, Labour stand out at 9/2. In effect, you are getting roughly 9/4 about them to finish in the top two, which looks generous given the dynamics of this race. If progressive voters hesitate over whether to back the Greens or Labour, a late squeeze could allow Labour to consolidate enough support to edge into second place — or even push for first if Reform underperforms expectations. That uncertainty on the left remains a key factor. Reform’s route to a top-two finish depends heavily on maximising turnout in their strongest areas while capitalising on a divided progressive vote. If turnout is softer than expected in those pockets, or if anti-Reform sentiment hardens late in the campaign, Labour are the most likely beneficiaries of that shift. Crucially, Labour do not need to win the by-election to land this bet — they simply need to outperform one of the other principal challengers. Given their established vote base, local organisation, and long-standing presence in the constituency, that is a realistic pathway. Even allowing for some erosion in parts of their support, Labour still retain a solid core vote. In a by-election — particularly one where turnout may be lower — party machinery, voter loyalty, and ground operation often carry more weight than campaign momentum alone.
Also take a look at our latest piece on the Gorton and Denton by-election, where we explore the potential value in the last-place finish and match-bets markets.