The return of SV will not transform regional politics overnight. But it does make mayoral contests more strategic, more coalition-minded and less predictable than before. And, in the short term, it might just save Labour’s skin in Greater Manchester.
Greater Manchester’s next mayoral contest may not lack for attention. If Andy Burnham does return to Westminster, the by-election to replace him would quickly become a national political story.
But amid the speculation over candidates, factions and what it all means for Labour, one of the most consequential details may be the one least likely to dominate the coverage: the voting system itself.
But to the trained eye, a seemingly simple technical change in how votes are cast and counted offers insight not just into how future elections will swing, but also into how future winners will govern.
The Government’s decision to reintroduce Supplementary Vote for mayoral elections, confirmed this week with little fanfare via an unassuming statutory instrument, is one of those moments.
On the face of it, this is a straightforward reversal. The previous Government moved mayoral contests to First Past the Post through the Elections Act 2022. Labour has now moved them back to Supplementary Vote, the system previously used for England’s metro mayors, the Mayor of London and Police and Crime Commissioners.
What has changed?
Under First Past the Post, the candidate with the most votes wins. Sometimes this works well and yields broadly proportional results, but it doesn’t take a politics scholar to see that, on occasion, this voting system can deliver heavily distorted electoral outcomes.
Just look at Labour’s monumental, Blair-rivalling, 170-seat majority in 2024 – the second highest ever achieved in the post-war era. This was done so on just 33.7% of the popular vote, the lowest vote share ever achieved by a governing party in that very same period.
Supplementary Vote (SV) works differently. Voters get a first and second preference. If no candidate wins more than 50% on first preferences, all but the top two are eliminated. The second preferences of eliminated candidates are then redistributed between the two remaining candidates.
The significance of SV is not simply that it changes how candidates win. It changes who can win. Success depends not just on mobilising loyal supporters, but on being acceptable to a broader range of voters whose first choice lies elsewhere. And that changes how candidates play politics.
Mayoral politics
The politics of mayoral elections is increasingly less like traditional local government, even national government perhaps, and more like presidential politics. In the established Strategic Authorities, these are high-profile roles with substantial budgets, executive power, and lots of ribbon-cutting.
Most importantly, Mayors are increasingly seen as individuals with personality rather than cookie-cutter party figures, in a way which simply is not true for MPs.
So the system used to elect them shapes behaviour.
Under First Past the Post, the incentive is to mobilise your base and hope the opposition is split. Under SV, the incentive shifts slightly. You still need a strong first preference vote, but you also need to be acceptable enough to other voters to pick up second preferences.
That changes campaign strategy. It rewards broader appeal, coalition-building and a more place-based political language. And those incentives do not disappear after election day. A mayor elected with substantial second-preference support has good reason to continue governing in a way that will keep that wider coalition together.
Which brings us to Greater Manchester
In news that was in equal measure completely shocking and wholly unsurprising, Andy Burnham is now eyeing up a leadership challenge. Whether that succeeds or not is another question. But if it does take him back to Westminster, Greater Manchester could face a mayoral by-election without the one person who has held its Labour coalition together for the best part of a decade.
Burnham’s coalition in GM is not simply a Labour vote. It is a Burnham vote. It brings together traditional Labour supporters, inner-city progressives, suburban moderates, soft Conservatives and generally people who may not love Labour nationally but think he has done a decent job locally. Having won every ward in Greater Manchester in the 2021 mayoral election, he almost repeated the sweep in 2024, taking 214 of the region’s 215 wards.
The problem for Labour is that this coalition does not and will not automatically transfer to whoever comes next. Many voters in inner city Manchester are likely to move to the Greens, some to the Liberal Democrats, some in the leafy GM suburbs on the edge of the region back to the Conservatives, and plenty of votes up and down the city region will undoubtedly go to Reform.
Reform’s base is much more solid, and its own vote is less splintered. Reform would not need to build a Burnham-style coalition across Greater Manchester. It would only need its own vote to hold while Labour’s vote split around it.
SV changes that. It gives Labour a chance to stitch parts of the Burnham coalition back together in the second round. Voters can give their first preference to another party but still use their second preference to prevent Reform from taking the mayoralty.
That does not guarantee Labour wins. But it does mean Reform has to do more than consolidate discontent. It has to prove it can win beyond its base.
What does all this mean?
The takeaway is that regional politics is becoming more fluid. Organisations engaging with combined authorities can no longer treat mayoral politics as a binary contest in which the winner takes all, can afford to ignore everyone else, and can rule with impunity.
It is not enough to understand the incumbent mayor’s priorities. You need to understand the wider political ecosystem around them. Who influences the mayoral narrative?
Which parties are shaping the debate from outside power? Where might second preferences come from? And what does all this mean for the billions of pounds in investment and funding that Strategic Authorities like GM will now be managing on an annual basis?
The real significance of SV is not that it changes the arithmetic. It changes the kind of politicians who can win. As England’s mayors acquire more powers, bigger budgets and greater public visibility, that distinction matters. The winners of future mayoral contests will not simply need the largest tribe, they will need the broadest coalition.
And, in the short term, it might just save Labour’s skin in Greater Manchester.
by Jonathan Conolly