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This piece by Sophie Stowers  and Paula Surridge on undecided voters is taken from our recent report “The state of public opinion: 2023”. Read the full report here.

Amongst all the talk of poll leads, by-election results and voting intentions, it is easy to forget about one important group: those who are still undecided. Polls indicate that around 16% of voters are currently ‘don’t knows’, a relatively consistent number compared to previous elections and in line with growing trends of weak partisanship and voter volatility.

The seemingly quite consistent overall number of ‘don’t knows’, combined with the shift in party support in polls since 2019, may make the next election seem like a foregone conclusion. But around 85% of this undecided group do plan to vote at the next election, and their votes could be crucial, not least in determining the margin of victory. It is certainly worth considering who exactly the undecideds are.

British Election Study data from May 2023 allows us to delve into their demographic makeup. Of those who say they do not know who they will vote for at the next election, most have above a GCSE-level education, with over 40% having a university degree. They are spread across social grades, though are slightly more likely to be lower middle or skilled working class and are scattered across the country. Undecided voters also tend to skew older, with over half aged 55 and above.

Despite this group’s relative demographic diversity, over half (55%) voted for Boris Johnson at the last election, with only 16% voting Labour. A partisan gap in the number of undecided voters is not a new phenomenon and was seen among former Labour voters in 2017.

Yet the gap between 2019 Conservative and Labour voters saying they are undecided is particularly wide. This suggests that a large portion of those still ‘up for grabs’ have drifted away from the Conservative party.

An earlier section demonstrates that recent scandals, from Partygate to Tentgate, have simply put off many voters from voting Conservative again. Not even half of 2019 Conservatives are planning to vote for the party again at the next election, with around 23% saying they do not yet know who they will vote for. Analysis from YouGov shows that, if Labour won over 11% of these ex-Tory voters, this would exceed the number of Labour voters Boris Johnson flipped in 2019.

These 2019 Conservative-2023 Don’t know voters tend to be mostly female, with around 75% being homeowners and 65% over the age of 55. The economy is a key issue to this group, with 65% citing this as the most important issue facing the country – slightly less than for those who have already switched their support to Labour.

There are two key mistakes to avoid when looking at this group of undecided voters. First, there is a presumption that many of these Conservative ‘don’t know’ voters are being pulled towards Reform. This group does share some demographic similarities with Conservative-Reform ‘defectors’ (both groups tend to be older homeowners). However, their policy preferences are very different. Just 15% of Conservative ‘don’t knows’ cite immigration as a key issue. Meanwhile, 59% of those now intending to vote Reform prioritise immigration, with issues such as crime and asylum also much more important to this group.

Conservative-to-Reform voters are also much less approving of Sunak (-37 net favourability) and Starmer (-89 net favourability) than Conservative ‘don’t knows’ (+7 and -55 respectively). These groups are not one and the same.

Indeed, data from Redfield and Wilton shows that many undecided voters are not leaning towards Reform, but rather to Labour, the Liberal Democrats or the Greens. Sunak therefore faces losing dissatisfied 2019 Conservatives not only to the right and Reform, but also to parties of the left.

A second mistake would be to assume that, at election time, many of these undecided 2019 Tory voters will simply ‘return home’ to the Conservative Party. Some presume that if voters have yet to cross the threshold and say they will vote for another party, they can be won back by those they voted for previously. Previous research shows that this did indeed occur for Theresa May in 2017 and, crucially, Jeremy Corbyn at the same election.

The number of 2019 Conservative ‘don’t knows’ has dropped since Sunak took over from Liz Truss in 2022. Data from Ipsos shows uncertain Conservatives are more likely to lean towards returning to the party than going elsewhere. These figures provide some evidence that, at an election, the Conservatives can reel some undecided voters back and eat into a Labour majority.

Yet this ignores two things. First, the decrease in ‘don’t knows’ among 2019 Conservative voters since Sunak took over can be attributed to a large shift towards Reform among them. Indeed, 78% of those intending to vote Reform at the next election voted Conservative in 2019.

Second, ‘home’ for many of those who voted Conservative in 2019 is not with Rishi Sunak. The voter coalition Boris Johnson built in 2019 hinged on Brexit.

This meant that we saw a lot of Leave voting, non-traditional Tories ‘lending’ their vote to the party in an attempt to ‘get Brexit done.’ Indeed, of those 2019 Conservatives who are now undecided, 16% voted UKIP in 2015, and 11% voted Labour in 2017. 47% say they have no affiliation with any particular party.

More widely, the shift of voters away from the Conservative Party to ‘don’t know’, ongoing since 2019, is worse than it was for Theresa May in 2017, and has not really shifted since Boris Johnson’s departure in 2022. Nor can it be guaranteed that undecided voters will turn out at an election – the fact they are not enthused enough to lean to any particular party hardly inspires confidence on that score.

The ‘don’t knows’ are an often-forgotten group whose votes will be crucial to the outcome of the next election. The fact that they seem ‘up for grabs’ from all sides and were such a crucial part of the government’s last electoral coalition, means parties will be targeting them – but quite where they’ll land seems yet to be determined.

By Sophie Stowers, Research Associate, and Professor Paula Surridge, Deputy Director, UK in a Changing Europe.


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