On Thursday 30 July, Greater Manchester will be electing a new mayor. The by-election follows Andy Burnham’s decision to return to Westminster, but it’s not just the mayor who will be changing. The way the voters of Greater Manchester choose their next Mayor will also change.
For the first time since it was abolished by the previous government, the traditional Supplementary Vote (SV) system will once again be used for mayoral elections.
How does the Supplementary Vote work?
Instead of voting for just one candidate, voters can mark a first choice and a second choice. If one candidate is the first choice of more than half of voters, they win immediately.
If nobody wins more than half, only the top two candidates stay in the contest. Rather than make everyone come back to pick between them, the ballots are checked again. If your first choice is one of the final two, your vote stays with them. If your first choice was knocked out, but your second choice is one of the final two, your vote is added to their total.
The Supplementary Vote is designed to stop vote splitting, which is when a large group of voters who all want roughly the same thing, split their vote between multiple candidates. If a smaller group all vote for the same candidate, that candidate can win, even though most people do not want their policies.
Under the Supplementary Vote, the winner is therefore the candidate who can build the broadest coalition of support, rather than simply the one who finishes first in a fragmented field.
Gerrymandering the voting system
The Supplementary Vote had been used since the creation of directly elected mayors in England with the Local Government Act 2000. Mayors exercise significant individual power, making decisions on transport, housing, policing and economic development, so you wouldn’t want them just to focus on benefiting a narrow core of voters.
Yet the previous government decided to impose First Past the Post for mayoral and Police and Crime Commissioner elections with the Elections Act 2022. Historically, the left has more parties than the right, giving the impression that this change was intended at the time to help the Conservatives win more Mayors.
Why First Past the Post was always a poor fit for mayors
First Past the Post works by electing whichever candidate receives the most votes, even if they fall far short of half of the voters. Last year, we saw exactly what that means in practice.
In Cambridgeshire & Peterborough, Conservative Paul Bristow was elected with just 28.36% of the vote. In the West of England, Labour’s Helen Godwin won with a mere 24.97%. Why should a quarter of voters impose their views on everyone else?
With recent rise of more parties on the right, it is no longer just the left that sees its vote split. This a timely reminder of the folly of choosing a voting system that benefits your party at one point in time, when voting patterns can change.
Thankfully, following a change of government, Parliament passed the English Devolution & Community Empowerment Act in 2025 which restored the Supplementary Vote. As a result, Manchester voters will once again be able to put a second choice on their ballot paper.
Why the Alternative Vote would be a better choice for Mayors
The Supplementary Vote works best when voters have a clear idea who the top two might be. But with five parties over 10% in the polls even the Supplementary Vote might not be able to handle the way we are voting.
A step in the right direction
The way we count the votes shapes the incentives for the candidates running for Mayor of Manchester, the choices available to voters and the legitimacy of the person elected. While the Supplementary Vote may not be perfect, it is a welcome move back to a system that values voter choice rather than limiting it – for this election and all Mayoral elections in future.
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