The Caerphilly by-election result saw the sudden rise of a pro-independence party and the devastating fall of the traditional, incumbent party. This result, coming ten years after the SNP’s historic routing of Labour in Scotland, hints that Wales could follow suit.
An unprecedented rise
Thursday, 23 October 2025 saw something both ground-breaking and ground-shaking. The voters of Caerphilly ousted Labour in a Senedd by-election, electing a Plaid Cymru candidate for the first time in the constituency’s history.
But it isn’t just the mere result that’s historic, it’s the scale of it. Plaid Cymru’s candidate, Lindsay Whittle won the seat from Labour with a 27% swing from Keir Starmer’s party. He saw his vote share increase by 19%, achieving 15,961 votes (47.4%) compared to the last Senedd election which saw Plaid Cymru achieve 8,211 votes (28.4%).
Reform UK Limited came second with 12,113 votes (36%), Labour came third with 3,713 votes (11%), the Conservatives came fourth with 690 votes (2%), the Greens achieved fifth place with 516 votes (1.5%), the Liberal Democrats came in sixth with 497 votes (1.5%), Gwlad in seventh with 117 votes (0.3%) and UKIP finished last with 79 votes (0.2%). The turnout was 50.4%.
A devastating fall
For the incumbent party, the result was a nightmare. The Labour Party, once so strong in Wales, lost Caerphilly; a seat they had held for its entire existence, and one that should have backed them to the hilt.
To drop from a mighty first to a meagre third means a lot more than a few bumps in the road. It speaks of an outright rejection of Keir Starmer’s record in government and a decisive defenestration of the party that put him there.
All look rather familiar?
You would be forgiven for thinking you’d seen this all before. The rise of a centre-left nationalist party, as a result of the fall of the centuries-old democratic socialist party, is a phenomenon which has played out before. A phenomenon with the same sorts of swings as we have seen in Caerphilly.
In 2015, the UK general election saw the Scottish National Party sweep the board in Scotland, taking swathes of seats from Labour and the Liberal Democrats, leaving them with only one MP apiece. The national swing was 23.9% from Labour to the SNP, a number which resonated with many of the constituencies and again in Caerphilly, a decade later.
Not everything is the same
However, not everything can draw a parallel with the 2015 general election in Scotland.
For a start, this was an election to a devolved parliament with a Labour-run government as opposed to a Westminster election. The incumbent devolved Labour administration will have borne the brunt of the voters’ fury for the actions of Keir Starmer’s government, at a UK level. Scotland already had a devolved SNP government at the time of the party’s victory in 2015.
Another major difference is that, in 2015, Reform UK did not exist. Farage did, in the form of UKIP but, as a party they failed to make a splash in Scotland. In Caerphilly, however, Reform UK stormed into second place with 36% of the vote, making the election a straight fight between left-wing Welsh nationalism and right-wing British nationalism. In Scotland, it was a straight fight between the SNP and Labour, while in Caerphilly, Labour finished as far from the fight as possible.
The ‘No’ referendum
In 2015, the SNP rose to historic heights on the back of the referendum on Scottish independence. The previous year had seen 1.6 million people in Scotland vote for independence. The energy carried on into the 2015 general election, where the SNP won seats across the entire nation, in nationalist and unionist areas alike. Wales has had no such referendum. This swing towards the nationalist party has been the result of a few things: the hope of Welsh independence, dissatisfaction with Labour, a wish for a left-wing representative, and a desire to stop the far-right Reform UK from gaining a foothold in Wales.
What will happen next?
It’s hard to say how this will play out at the 2026 Senedd election. Opinion polling at the time of writing, shows it is still at a three-way fight between Labour, Plaid Cyrmu and Reform UK. Each one has taken a lead, but they have also lost it such advances before. Based on this, with each party jockeying for position, it’s anyone’s guess as to how the election will play out.
It must also be noted that, just because Plaid Cymru won the by-election with an impressive swing, it doesn’t necessarily follow that they will hold the seat at the next Welsh election. In 2008, the SNP won Glasgow East from Labour in a UK parliamentary by-election with a 22.5% swing, only for the seat to return to Labour at the general election in 2010. That said, Plaid Cymru are equally likely to retain the seat.
A monumental victory for Plaid Cymru, a devastating loss for Labour and a hopeful rejection of the far-right in Reform UK’s loss. In the Caerphilly by-election, it certainly appears that Wales is following in Scotland’s 2015 footsteps. But will the Welsh nation do this at the next Senedd election? Will Wales, as with Scotland, elect a nationalist government in preference to the UK-wide parties? Or will Labour continue to rule in the Senedd? More worryingly, will Reform UK get their hands on the levers of power in Cardiff? Only time will tell.
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