Small swings, high drama: why UK polls are less volatile than they seem – in charts
In what is increasingly appearing as a fragmented five-party system, small swings in polling data carry significant political consequences.
Cabinet reshuffles, party infighting, policy reversals, by-elections, defections, and seemingly large swings in support have made the UK’s political news cycle particularly intense recently.
However, a close examination of polls since last year’s local elections reveals that remarkably little has changed overall.
While some individual polls have shown noticeable shifts, most movements have been limited to a few percentage points. The major parties remain roughly where they were, and Reform has maintained a comfortable lead for nearly a year.
As the local elections approach in May, analysts will scrutinize the polls more closely to assess how these shifts might translate into electoral swings and their broader implications.
This dynamic became even clearer as Nigel Farage potentially underestimated Reform’s support, indicating that he values polling coverage as a means to increase visibility for his insurgent party.
So, why do the polls appear so volatile?
These charts illustrate how, in what appears to be a five-party system, small movements can lead to dramatic political outcomes, even as the fundamental balance between left and right remains relatively stable.
Headline numbers haven’t moved much
Every poll includes a margin of error, often two or three points, which can produce quite different headline results in a close multiparty contest. This means that individual polls should be interpreted cautiously, with more emphasis placed on longer-term trends in the overall average of polls.
Since the last local elections, changes in the main political parties’ polling ratings have been modest.
Labour’s decline and the Conservatives’ fluctuations are within the normal range of polling variation over a year.
Fragmentation changes the meaning of small swings
Experts argue that the UK no longer operates within a traditional two-party framework.
Five parties now poll at significant national levels: Labour, the Conservatives, Reform, the Liberal Democrats, and the Greens. This is alongside the SNP in Scotland and Plaid Cymru in Wales.
Joe Twyman, founder and director of the public opinion consultancy Deltapoll, explained that this creates a complex picture:
“A five-party system makes polling more difficult. It amplifies a lot of the problems that pollsters were already facing.”
Twyman added that instability often accompanies sharp surges in popularity for parties 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, even a two-point swing can be highly significant, potentially altering entire races.
A shift of a couple of points nationally could move Labour between second and fourth place, elevate the Greens to second, bring Reform and Labour into a neck-and-neck contest, or push the Conservatives into a clear second position.
Over the past month, Labour, the Conservatives, and the Greens have each occupied second place in individual polls. In these polls, the gap between the second- and third-placed parties has been no more than five points.
Wider voter blocs are stable …
Examining broader left-wing and right-wing party groupings shows little change in polling support.
Combined support for left-leaning parties (Labour, the Liberal Democrats, and the Greens) has remained between 43% and 47% since January 2025.
While the Liberal Democrats have attracted some wavering Conservative voters, particularly in southern England, they position themselves on the progressive side of politics.
Meanwhile, the right-leaning bloc (the Conservatives and Reform) has hovered between 44% and 49%.
Since 2013, when consistent data became available, the left-wing bloc has ranged between 40% and 66%, while the right-wing bloc has ranged between 29% and 54%.
Movement between these blocs is significantly less when excluding the years 2021 to 2024, which saw large swings in public support following major political events.
Although the progressive parties SNP and Plaid Cymru have substantial support in Scotland and Wales, they have been excluded from this analysis due to data limitations and because they do not contest elections across the entire UK.
Jane Green, professor of politics at Oxford University, highlighted the stability of these blocs over time, stating:
“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
Green noted a decline in Labour and Conservative dominance within their respective blocs:
“What we’re seeing is the leftwing bloc fragmenting and the rightwing bloc is consolidating towards Reform.”
Throughout 2025, Labour’s share of the collective left-wing vote fell from 56% to 39%, a drop of 17 points.
This decline coincided with a shift of some voters to the Greens, which increased their share of the left-wing vote to 32%, up 14 points over the year.
At the start of 2025, the Conservatives held 50% of the collective right-wing vote, but this had dropped to 40% by December 2025.
Three in five individuals who identified with a right-wing party in polls said they supported Reform. This represents the highest level for a non-Conservative right-wing party in over a decade.
Prof Sir John Curtice, of the University of Strathclyde, explained:
“There are the two blocs – and most of the movement is between either Conservative-Reform or between Labour-Green-Lib Dem.”
In recent by-elections in Gorton and Denton, the vote fractured on both the left and right, with Plaid Cymru and the Greens winning seats on the left, and Reform securing second place on the right. In Gorton and Denton, the two insurgent parties collectively won 69.4% of the vote.
Green suggested that compared with previous elections, different parties may represent these blocs across various constituencies:
“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
The UK’s first-past-the-post electoral system involves 650 separate constituency races. With the rise of Reform and the Greens, many seats are now contested by three or four parties, resulting in narrower winning margins.
Twyman noted:
“Individual constituency polling is costly and difficult so we use methods like multilevel regression and post-stratification (MRP) 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 MRP analyses – by More in Common and Find Out Now/Electoral Calculus – both estimated Reform’s vote share at 31%. However, More in Common forecast Reform winning 381 seats, compared with 331 seats predicted by the other, a substantial difference between a strong or fragile majority.
Prof Curtice explained:
“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 Liberal Democrats are geographically concentrated in southern England, whereas Reform’s support is more evenly spread.
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 Conservatives for decades could become its undoing.”
Higher levels of voter switching
Voter volatility remains historically high, with more people indicating they might switch parties than in previous decades.
However, much of this switching occurs within voter coalitions, meaning the overall balance between left and right does not change dramatically.
Prof Green stated:
“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 the UK is currently in the midst of a transition from establishment to insurgent parties within the two major voter blocs.
This is part of a longer-term trend of increased voter fluidity, now intensified as two charismatic leaders – Zack Polanski and Nigel Farage – seek to capitalize on disillusionment with the two major parties.
Prof Curtice warned that history offers limited guidance on the future:
“We have never had five-party politics before. We’re in unprecedented territory and none of us know exactly where this will go.”
