Small swings, high drama: why UK polls are less volatile than they seem – in charts

6 hours ago 9

Cabinet reshuffles, party infighting, policy reversals, byelections, defections and apparently huge swings in support – the UK’s political news cycle feels especially relentless at the moment.

But if you look closely at the polls since last year’s local elections, remarkably little has changed.

While there have been some noticeable individual polls, most movements have been limited to a small number of percentage points. The big parties are roughly where they were. Reform has had a comfortable lead for almost a year.

As the local elections loom in May, analysts will be scrutinising the polls more closely – testing how these shifts will translate into electoral swings and the extent to which Keir Starmer’s Labour will struggle.

This became even more apparent as Nigel Farage complained about YouGov’s methodology potentially underestimating Reform’s support, suggesting that he values polling coverage as a way to drive increased coverage of his insurgent party.

So why do the polls feel so volatile?

These charts show how, in what is looking like a fragmented five-party system, small movements can produce dramatic political consequences – even as the underlying balance between the left and right remains relatively stable.


Headline numbers haven’t moved much

Every poll has a margin of error, often of two or three points – a number that can produce quite different headline results in a close multiparty contest. This means that we shouldn’t pay too much attention to any one poll – rather, look at the longer-term shifts in the overall average of polls.

Since the 2025 local elections, the changes on the main political parties’ polling ratings have been muted.

Chart showing polling shifts across the last year have been limited

Labour’s drop and the Greens’ gain are notable, but these swings are quite normal in polling across an entire year.


Fragmentation changes the meaning of small swings

Experts argue that the UK is no longer operating in a two-party environment.

Five parties now poll at meaningful national levels: Labour, the Conservatives, Reform, the Lib Dems and the Greens. This is alongside the SNP in Scotland and Plaid Cymru in Wales.

Chart showing UK polling averages over time

Joe Twyman, the founder and director of the public opinion consultancy Deltapoll, said that this helps create a confusing picture: “A five-party system makes polling more difficult. It amplifies a lot of the problems that pollsters were already facing.”

Exacerbating the problem, Twyman says, is the instability that often goes along with a sharp surge in popularity for a party that was previously on the fringes. “Some of these parties are on the rise. Parties like the Greens and Reform have new support, so that creates uncertainty. How do we precisely gauge the popularity of these new movements?”

In a five-party system, a two-point swing becomes much more significant as it can alter entire races.

A shift of a couple of points nationally could move Labour between second to fourth, put the Greens into second, bring Reform and Labour neck-and-neck, or push the Conservatives into a clear second.

Chart showing how close polls, and disagreement between pollsters, resulted in three different second-placed parties in one month

Over the past month, Labour, the Conservatives and the Greens have each been in second place in individual polls. In each of these polls, the gap between the second- and third-placed party has been no more than five points.


Wider voter blocs are stable …

Looking at the broader leftwing and rightwing groups of parties, there has been little shift in the polls.

Combined support for left-leaning parties (Labour, the Lib Dems and the Greens) has remained between 43% and 47% since January 2025.

While the Lib Dems have appealed to wavering Conservative voters, especially in the south of England, overall they position themselves on the progressive side of politics.

Meanwhile, the right-leaning bloc (the Conservatives and Reform) has hovered between 44% and 49%.

Chart showing support for the leftwing and rightwing blocs since the general election

Since 2013, which is when PollBase has consistent data from, the leftwing bloc has shifted between 40% and 66%, while the rightwing bloc has shifted between 29% and 54%.

The movement between these groups is significantly less when you exclude the years 2021 to 2024, when there were big swings in public support after the pandemic and partygate.

Chart showing how support for the left-wing and right-wing blocs over time

While the progressive parties SNP and Plaid Cymru have significant support in Scotland and Wales, they have not been included due to data availability and the fact that they do not stand for election across the whole of Britain.

Jane Green, professor of politics at Oxford University, pointed to the fact that these blocs of voters have stayed broadly stable over time to argue: “What’s going on isn’t random at all. It’s highly structured.

“There is a huge amount of stability across the structure of the two blocs. They have the same demographic structure as before.”


… but the leadership of these blocs is changing

There has been a decline in Labour and the Conservatives’ dominance over their respective blocs, says Green: “What we’re seeing is the leftwing bloc fragmenting and the rightwing bloc is consolidating towards Reform.”

Over 2025, Labour’s share of the leftwing parties’ collective vote share declined from 56% to 39% – a drop of 17 points.

This came as some leftwing voters switched to the Greens, which commanded 32% of the collective leftwing vote – an increase of 14 points over the year.

Chart showing how Labour’s dominance of the left-wing has slipped in the last two years

At the turn of 2025, the Conservatives held 50% of the collective rightwing vote – but this had dropped to 40% by December 2025.

Three in five people who picked a rightwing party in the polls said they supported Reform. This is the highest level for a non-Conservative rightwing party for over a decade.

Chart showing how Farage’s parties have often had more than a fifth of the right-wing bloc - but now Reform has the majority

Prof Sir John Curtice, of the University of Strathclyde, said: “There are the two blocs – and most of the movement is between either Conservative-Reform or between Labour-Green-Lib Dem.”

In the recent byelections in Caerphilly, then Gorton and Denton, the vote fractured both to the left, with Plaid Cymru and the Greens winning the seats, and to the right, with Reform claiming second place in both seats. In Gorton and Denton, the two insurgent parties collectively won 69.4% of the vote.

Green argued that, compared with previous election cycles, it is likely that we could see different parties representing these blocs across different constituencies.

Pointing to the importance of tactical voting, she added: “What we might see is that people still identify with being on the right or left, but being more willing to switch within those sides.”


First-past-the-post amplifies volatility

Under first-past-the-post, the UK runs 650 separate constituency races. With the rise of Reform and the Greens, many seats are now three- or four-way contests with thinner winning margins.

Twyman noted: “Individual constituency polling is costly and difficult so we use methods like MRP [multi-level regression and post-stratification] modelling to replicate it. But this doesn’t take into account hyper-local factors. And when parties are winning seats on 20 to 25% of the vote, in five-party races, any small swings – including those caused by hyper-local factors – become more significant.”

Two recent MRPs – by More in Common and Find Out Now/ Electoral calculus – both had Reform on 31% of the vote. However, More in Common forecast Reform would win 381 seats, compared with the predicted 331 seats in the other – a huge difference between a strong or fragile majority.

Chart showing how Reform are polling at less than a third of the vote - but some MRPs suggest this gives them a majority

Prof Curtice said that “under first-past-the-post, there are no rules dictating the relationship between a party’s share of the vote and share of the seats. The crucial thing is that it all depends on geography.

“A swing of two points between two parties which are both geographically distributed across the country is very significant. It’s not so important if the two parties are focused in specific geographical areas.”

The Lib Dem vote is geographically concentrated around the south of England, compared with Reform’s, which is more spread out.

Prof Curtice added: “If you are first, you want to have a geographically-even spread of your vote. But if you are second or third, you want a geographically concentrated spread.

“The system that was the ballast of the two-party system for decades could become its undoing.”


Higher levels of voter switching

Voter volatility remains historically high, with more people saying they might switch parties than in previous decades.

But a lot of this switching is people moving within their voter coalitions, meaning that the overall balance of left and right doesn’t hugely change.

Chart showing how there has been a long-term rise in volatility as voters begin to turn away from major parties

Prof Green said: “There is greater churn among voters, and that’s increasing between elections. It hasn’t been the majority of people, but it’s increasing. The broad trajectory is moving towards switching parties, with a greater proportion of people wanting to reject the major parties.”

Green argued that we are now in the middle of this movement from establishment to insurgent parties, within the two major voter blocs.

It is part of a longer-term trend of increased voter fluidity, but now appears to have come to a head as two charismatic leaders – Zack Polanski and Nigel Farage – seek to capitalise on the feeling of disillusionment with the two major parties.

Warning that history doesn’t give us clues on where we are heading, Curtice said: “We have never had five-party politics before. We’re in unprecedented territory and none of us know exactly where this will go.”

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