Plaid Cymru achieved a historic victory in the Caerphilly by-election on October 23, 2025, defeating Reform UK and dealing Labour its first parliamentary defeat in the constituency for over 100 years. Lindsay Whittle, the 72-year-old Plaid Cymru candidate and former council leader, secured 47.4% of the vote with a majority of 3,848, marking a seismic shift in Welsh politics just seven months before the crucial May 2026 Senedd elections. This comprehensive guide covers the complete by-election results, exit polls, what happened, who the key players are, what Plaid Cymru represents, and the profound implications for Labour, Reform UK, and the future of Welsh governance.
Caerphilly By-Election Results 2025
The official results announced on October 24, 2025, revealed a stunning political upset that sends shockwaves through the Welsh political establishment:
Final Results:
Lindsay Whittle (Plaid Cymru) – 15,961 votes (47.4%) – WINNER
- Change: +19.0% from 2021
Llŷr Powell (Reform UK) – 12,113 votes (36.0%)
- Change: +34.2% from 2021
Richard Tunnicliffe (Labour) – 3,713 votes (11.0%)
- Change: -34.9% from 2021
Gareth Potter (Conservative) – 690 votes (2.0%)
- Change: -15.3% from 2021
Gareth Hughes (Green Party) – 516 votes (1.5%)
- Change: New candidate
Steven Aicheler (Liberal Democrats) – 497 votes (1.5%)
- Change: -1.2% from 2021
Anthony Cook (Gwlad) – 117 votes (0.3%)
- Change: New candidate
Roger Quilliam (UKIP) – 79 votes (0.2%)
- Change: New candidate
Majority: 3,848 (11.4%)
Turnout: 33,689 votes (50.43% of 66,895 registered electors)
Swing from Labour to Plaid Cymru: 27%
The result represents a political earthquake, with Labour collapsing from 46% in 2021 to just 11%, finishing in third place behind Reform UK. Plaid Cymru’s surge from 28.4% to 47.4% demonstrates the party capitalizing on Labour’s weakness while simultaneously preventing Reform UK from achieving what would have been a landmark victory for Nigel Farage’s party.
Understanding the Historic Context
To appreciate the magnitude of this result requires understanding Caerphilly’s political history. Labour has held the Caerphilly constituency continuously since its creation in 1918 at the UK parliamentary level, representing over 100 years of unbroken Labour representation. At the Senedd level since devolution began in 1999, Labour has similarly dominated, never relinquishing the seat through six consecutive elections.
This electoral dominance reflects Caerphilly’s history as a traditional South Wales valleys constituency, forged in coal mining communities where Labour became synonymous with working-class representation and trade union politics. The constituency’s industrial heritage created deep cultural and political ties to the Labour Party that persisted long after the mines closed and economic structures transformed.
The 2021 Senedd election saw Labour’s Hefin David win with 13,289 votes (46%), maintaining the party’s hold with a comfortable 17.6% majority over Plaid Cymru’s second-place 28.4%. David’s tragic death on August 12, 2025, triggered the by-election, creating an unexpected electoral test for all parties just months before the scheduled May 2026 Senedd elections.
The dramatic swing of 27% from Labour to Plaid Cymru represents one of the largest party-to-party swings in modern Welsh electoral history. For Labour to collapse from first place with 46% to third place with 11% in just four years defies normal electoral gravity, suggesting fundamental realignment in Welsh politics rather than temporary protest voting.
Who Is Lindsay Whittle?
Lindsay Whittle, the 72-year-old victor, represents perseverance incarnate in Welsh politics. This marks his 14th time standing for election as a Plaid Cymru candidate since 1983, having previously run unsuccessfully 13 times before finally achieving victory. His emotional response when the results were announced – crying openly as the scale of his victory became clear – reflected decades of disappointment finally culminating in historic triumph.
Whittle has served as a Caerphilly County Borough councillor for nearly 50 years, accumulating unparalleled knowledge of local issues, community concerns, and constituent needs. His experience includes serving as leader of Caerphilly Council when Plaid Cymru controlled the local authority, demonstrating his administrative capabilities and leadership skills beyond merely winning votes.
The decision to select Whittle as Plaid Cymru’s candidate initially raised eyebrows given his age and previous electoral failures. However, his deep local roots, name recognition built over decades of council service, and genuine connection to the community proved decisive against younger, less-established opponents. Voters chose experience, authenticity, and proven local commitment over novelty or national party machinery.
In his emotional victory speech, Whittle paid tribute to Hefin David, the late Labour MS whose death triggered the by-election. “Hefin David’s kindness was the guiding spirit of my campaign,” Whittle stated, acknowledging the difficult circumstances under which the election occurred. This gracious tribute demonstrated the personal respect between political opponents even amid fierce party competition.
Whittle’s message to supporters emphasized both celebration and forward-looking determination: “We’ve beaten billionaire-backed Reform and, with the same determination, we can do it again in May 2026.” This framing positioned the by-election not as isolated victory but as proving ground for the crucial Senedd elections ahead, where Plaid Cymru harbors genuine ambitions of displacing Labour as Wales’ governing party.
What Is Plaid Cymru?
For readers unfamiliar with Welsh politics, understanding Plaid Cymru proves essential to contextualizing this victory. The party name “Plaid Cymru” translates from Welsh as “Party of Wales,” with “Plaid” meaning “party” and “Cymru” meaning “Wales.” The organization represents Wales’ principal nationalist political party, founded in 1925 with the primary goal of promoting Welsh culture, language, and ultimately achieving Welsh independence or enhanced autonomy within the United Kingdom.
Plaid Cymru’s ideology combines Welsh nationalism with center-left to left-wing policies on economic and social issues. The party advocates for protecting and promoting the Welsh language, transferring additional powers from Westminster to the Senedd, environmental protection, social justice, and ultimately achieving independence for Wales similar to Scotland’s constitutional aspirations. This positions Plaid as Wales’ rough equivalent to the Scottish National Party, though historically less electorally successful.
The party has participated in Welsh governance, most notably entering coalition with Labour to form the Welsh Government from 2007-2011 under the “One Wales” agreement. This coalition experience demonstrated Plaid’s capacity for practical governance beyond opposition rhetoric, though it also exposed tensions between nationalist principles and the compromises required in power-sharing arrangements.
Current Plaid Cymru leader Rhun ap Iorwerth, who became leader in June 2023, represents the party’s latest attempt to broaden appeal beyond traditional Welsh-speaking strongholds in northwest and southwest Wales into industrial South Wales valleys constituencies like Caerphilly. Ap Iorwerth’s leadership emphasizes economic competence, practical policies addressing cost-of-living concerns, and positioning Plaid as a credible alternative government rather than merely a protest party or single-issue nationalist movement.
The Caerphilly victory represents Plaid Cymru’s most significant breakthrough in the South Wales valleys, historically Labour’s impregnable heartland. Previous Plaid strength concentrated in rural Welsh-speaking areas and specific urban constituencies like Cardiff and Swansea, but Caerphilly’s industrial character and predominantly English-speaking population make this victory particularly significant for demonstrating broadened appeal.
Reform UK’s Strong Second Place
Reform UK’s 36% vote share and second-place finish, while falling short of victory, represents remarkable growth from just 1.7% (495 votes) in 2021. The party’s 34.2% increase marks the most dramatic surge of any party, though insufficient to overcome Plaid Cymru’s established local presence and organizational infrastructure.
Reform UK, led nationally by Nigel Farage, represents the latest incarnation of right-wing populist politics in Britain following UKIP’s decline. The party campaigns on immigration control, opposition to “woke” policies, skepticism toward climate change initiatives, reduced taxation, and criticism of mainstream political establishment corruption and incompetence. Reform’s messaging resonates particularly with disaffected working-class voters who previously supported Labour but feel abandoned by the party’s perceived shift toward metropolitan progressive values.
Llŷr Powell, Reform’s 36-year-old candidate, ran an energetic campaign that attracted significant national attention and resources. Nigel Farage himself visited Caerphilly multiple times, drawing large crowds and generating media coverage that raised Reform’s profile. The party’s campaign emphasized local cost-of-living concerns, NHS waiting times, and criticism of both Labour’s Welsh Government record and broader UK Labour policies under Keir Starmer.
Despite the defeat, Powell maintained optimistic rhetoric, claiming “Reform UK will form the next Welsh government” and characterizing the result as foundation-building for the May 2026 elections. “Our grassroots campaign will only get better,” Powell insisted, arguing that increased turnout demonstrated voters now had “a party they can trust” beyond traditional Labour-Plaid competition.
The result disappointed Reform strategists who had identified Caerphilly as potential breakthrough territory where Labour weakness and working-class demographics created optimal conditions for Reform’s populist messaging. Pre-election polls suggested a much closer contest between Reform and Plaid, with some predictions favoring Reform victory. The actual margin suggests polling either miscalculated Plaid’s ground game advantages or failed to capture late-deciding voters breaking toward Plaid rather than Reform.
Nigel Farage blamed Labour’s collapse for Reform’s defeat rather than Plaid’s strength, tweeting that “Labour voters deserted them” but chose Plaid over Reform. This interpretation positions Reform as fundamentally challenging Labour rather than competing across the political spectrum, though the reality that Plaid attracted former Labour voters complicates this narrative.
Labour’s Catastrophic Collapse
Labour’s third-place finish with just 11% represents nothing short of catastrophic failure in what should be safe territory. The party that has governed Wales continuously since devolution began in 1999 and held Caerphilly for over a century suffered humiliating rejection from voters, losing nearly 10,000 votes and seeing its vote share plummet by 34.9 percentage points.
Richard Tunnicliffe, Labour’s candidate, faced an impossible task defending a seat under siege from both left and right simultaneously. Plaid Cymru attacked from the left criticizing Labour’s Welsh Government record on NHS Wales waiting times, economic development, and perceived abandonment of working-class communities. Reform UK attacked from the right on immigration, cultural issues, and general “establishment” failure. Squeezed between these forces while shouldering responsibility for both Welsh and UK Labour governments’ unpopularity, Tunnicliffe’s campaign never gained traction.
Welsh First Minister Eluned Morgan, who leads the Labour Welsh Government, congratulated Whittle while acknowledging Labour’s accountability: “We are listening, learning lessons, and will come back stronger.” This somber response recognizes the severity of defeat while attempting to frame it as correctable through policy adjustments rather than fundamental political realignment.
However, the scale of Labour’s collapse suggests deeper problems than specific policy failures or campaign weaknesses. The result indicates potential fundamental breakdown in Labour’s traditional coalition, with working-class voters who historically formed the party’s base now splitting between Plaid Cymru’s social democratic alternative and Reform UK’s populist insurgency.
The by-election leaves Labour with just 29 of 60 Senedd seats, falling short of the 31-seat majority required for comfortable governance. This minority position complicates the critical January 2026 budget vote, requiring Morgan’s government to negotiate opposition support to pass spending plans. Labour has initiated discussions with other party leaders to secure necessary votes, though the political dynamics have shifted dramatically following Caerphilly’s verdict.
UK Prime Minister Keir Starmer expressed being “deeply disappointed” by the result, though avoided detailed analysis that might inflame Welsh Labour-London Labour tensions or undermine Morgan’s position ahead of the May elections. The result adds to broader Labour concerns following disappointing local election results in England and Scotland, suggesting the party’s 2024 general election victory hasn’t translated into sustained voter enthusiasm.
Exit Polls and Pre-Election Predictions
Pre-election polling suggested a much closer contest than the actual result delivered, with most predictions forecasting a tight two-way race between Reform UK and Plaid Cymru, with Labour distant third. The Times explicitly predicted potential Reform victory, while other analysts cautioned that the race remained too close to call given the unprecedented three-way competition dynamics.
Exit polls conducted on election day are not standard practice for Senedd by-elections due to cost and resource constraints, meaning final results arrived without the preliminary indication exit polls provide in major elections. This created additional suspense on election night as all parties waited for actual vote counts rather than having early indication of likely outcomes.
The polling challenges reflected unprecedented electoral volatility, with traditional voting patterns breaking down and large numbers of undecided voters making predictions uncertain. Pollsters struggled to model likely turnout accurately, with the eventual 50.43% significantly exceeding expectations and representing the highest turnout for any Senedd by-election since devolution began.
The polls’ underestimation of Plaid Cymru’s final margin and overestimation of Reform UK’s competitiveness likely reflected several factors including Plaid’s superior ground game converting wavering voters, late-breaking sentiment favoring Plaid among anti-Reform voters seeking to block Farage’s party, and potential shy Plaid voters understating their support to pollsters.
The Senedd and Welsh Parliament Context
For readers unfamiliar with Welsh governance, the Senedd represents Wales’ devolved parliament, equivalent to the Scottish Parliament or Northern Ireland Assembly. Established in 1999 as the National Assembly for Wales, the institution was renamed “Senedd Cymru” or simply “Senedd” in 2020, with “Senedd” being the Welsh word for “parliament.”
The Senedd consists of 60 Members of the Senedd (MS), previously called Assembly Members (AM), elected for five-year terms. The institution holds legislative powers over devolved matters including health, education, economic development, environment, agriculture, culture, housing, and local government. Reserved matters including defense, foreign affairs, immigration, and most taxation remain with the UK Parliament at Westminster.
The Welsh Government, led by the First Minister, exercises executive authority over devolved policy areas, making the Senedd crucial to Welsh life despite Westminster’s continuing sovereignty over the United Kingdom as whole. Labour has governed Wales continuously since devolution began, either with overall majority or through coalition/confidence arrangements with other parties.
The May 2026 Senedd election will be conducted under new electoral rules expanding the Senedd from 60 to 96 members and introducing closed list proportional representation. These reforms mean Caerphilly’s by-election represents the last Senedd by-election under current rules, with future vacancies filled from party lists rather than through by-elections.
Rhun ap Iorwerth and Plaid Cymru’s Leadership
Rhun ap Iorwerth became Plaid Cymru leader in June 2023 following Adam Price’s resignation after poor 2021 Senedd election results and internal party difficulties. The 52-year-old former BBC Wales journalist brought fresh energy and media-savvy communication skills to a party seeking to broaden appeal and present itself as credible alternative government.
Ap Iorwerth’s leadership emphasizes economic competence, practical policy proposals addressing cost-of-living concerns, and positioning Plaid as Welsh patriotic party transcending traditional left-right divides. His background as respected broadcaster provides credibility and communication ability that helps Plaid reach voters beyond its traditional base.
Following the Caerphilly victory, ap Iorwerth declared that voters had “chosen hope over division and progress over the stale status quo, backing Plaid Cymru’s positive, pro-Wales vision.” This framing attempts to position Plaid as optimistic alternative to both Labour’s perceived stagnation and Reform UK’s divisive populism, appealing to voters seeking change without embracing Farage’s brand of politics.
Ap Iorwerth now faces the challenge of transforming Caerphilly’s breakthrough into sustained momentum capable of seriously challenging Labour across Wales in May 2026. Plaid’s ultimate ambition involves winning enough seats to displace Labour as largest party and lead the next Welsh Government, either alone or in coalition. The Caerphilly result demonstrates this ambition may not be entirely fanciful, though converting by-election success into general election victory requires overcoming significant obstacles.
What This Means for the May 2026 Senedd Elections
The Caerphilly by-election serves as crucial barometer for the May 2026 Senedd elections, though translating by-election results into general election predictions requires caution. By-elections traditionally see protest voting, lower turnout, and dynamics that don’t replicate in general elections when voters choose governments rather than sending messages.
However, the scale and nature of Caerphilly’s result suggests potential genuine realignment rather than mere protest. Psephologist John Curtice told BBC Radio 4 that the result indicated Plaid Cymru were “best placed to win” the upcoming Senedd election, with Labour in “severe trouble.” This authoritative assessment from Britain’s leading election analyst carries significant weight.
For Labour, the result sounds alarm bells about their Welsh heartlands’ vulnerability. If Caerphilly—a seat Labour has held for over 100 years—can fall this dramatically, no Welsh Labour seat can be considered truly safe. The party faces existential questions about whether it can recover sufficiently in seven months to defend its 26-year governance of Wales.
For Plaid Cymru, Caerphilly provides momentum and credibility. The party can now claim to be the primary challenger to Labour across Wales, capable of winning even in the valleys where Labour dominance appeared permanent. This strengthens fundraising, volunteer recruitment, and media positioning heading into the crucial election campaign.
For Reform UK, the strong second place demonstrates the party’s potential in Wales while highlighting the challenges of converting polling numbers and media attention into actual electoral victories. Reform faces decisions about resource allocation, message refinement, and whether to emphasize head-to-head competition with Labour versus positioning itself as distinctly different from all established parties including Plaid.
The new Senedd electoral system complicates predictions, with the shift to closed list PR and expansion to 96 members creating uncertainty about how by-election results translate. However, the fundamental message about voter dissatisfaction with Labour and appetite for change remains valid regardless of electoral mechanics.
What Happens Next in Welsh Politics
The immediate aftermath focuses on the January 2026 budget vote, where Labour’s minority government must secure opposition support to pass its spending plans. Plaid Cymru and other opposition parties now hold enhanced leverage to extract policy concessions or modifications in exchange for budget support.
Negotiations between Morgan’s Labour government and opposition leaders will determine whether compromise can be reached or whether budget deadlock creates governance crisis. The political dynamics have shifted dramatically, with Labour’s weakened position emboldening opposition parties to demand substantive changes rather than merely offering procedural support.
Beyond budget negotiations, all parties enter intensive election preparation mode for May 2026. Labour must diagnose what went wrong in Caerphilly and develop strategies to prevent repetition across Wales. Plaid must build on Caerphilly momentum while articulating comprehensive governing vision. Reform must refine messaging to convert polling numbers into votes. Conservatives face existential crisis having fallen to 2%, while Liberal Democrats remain marginalized.
The campaign will focus heavily on NHS Wales performance, cost-of-living issues, economic development, and broader questions about Welsh governance quality after 26 years of Labour control. Plaid will emphasize the need for change and fresh ideas, Labour will warn against risk and instability, while Reform attacks all established parties as corrupt and incompetent.
Frequently Asked Questions
What were the Caerphilly by-election results?
Plaid Cymru’s Lindsay Whittle won with 15,961 votes (47.4%), defeating Reform UK’s Llŷr Powell who received 12,113 votes (36.0%). Labour’s Richard Tunnicliffe finished third with just 3,713 votes (11.0%), suffering a catastrophic 34.9% decline from 2021. The turnout was 50.43%, the highest for any Senedd by-election.
When was the Caerphilly by-election held?
The Caerphilly by-election took place on October 23, 2025, with results announced the following day on October 24. The election was triggered by the death of Labour MS Hefin David on August 12, 2025.
Who is Lindsay Whittle?
Lindsay Whittle is a 72-year-old Plaid Cymru politician who has served as a Caerphilly County Borough councillor for nearly 50 years and previously led the council. This was his 14th time standing for election, having been unsuccessful 13 times previously before achieving his historic victory.
What is Plaid Cymru?
Plaid Cymru means “Party of Wales” in Welsh. It is Wales’ principal nationalist party, founded in 1925, advocating for Welsh culture, language protection, enhanced Welsh autonomy or independence, and center-left to left-wing policies on economic and social issues. Current leader is Rhun ap Iorwerth.
Why did Labour lose Caerphilly?
Labour suffered a 34.9% vote share collapse due to multiple factors including dissatisfaction with both Welsh and UK Labour governments, NHS Wales performance concerns, cost-of-living issues, perceived abandonment of working-class voters, and effective campaigns by both Plaid Cymru and Reform UK exploiting Labour’s vulnerabilities from different political directions.
What does this mean for Welsh politics?
The result suggests potential fundamental realignment in Welsh politics, with Labour’s century-long dominance under serious threat. Plaid Cymru emerges as credible alternative government ahead of May 2026 Senedd elections, while Reform UK demonstrates significant strength. Labour now governs with minority of 29 of 60 Senedd seats.
What is the Senedd?
The Senedd is Wales’ devolved parliament, established in 1999 and renamed from National Assembly for Wales in 2020. It consists of 60 Members of the Senedd (MS) with legislative powers over health, education, economy, environment, and other devolved matters. Elections occur every five years with next scheduled for May 2026.
Who is Rhun ap Iorwerth?
Rhun ap Iorwerth is Plaid Cymru’s leader since June 2023. The 52-year-old former BBC Wales journalist brings media expertise and focuses on presenting Plaid as credible alternative government emphasizing economic competence and practical policies rather than just nationalist identity politics.
When are the next Welsh elections?
The next Senedd elections are scheduled for May 2026. This will be conducted under new electoral rules expanding the Senedd from 60 to 96 members and introducing closed list proportional representation, fundamentally changing Welsh electoral politics.
What is Reform UK’s position in Wales?
Reform UK achieved 36% in Caerphilly, demonstrating significant potential in Wales despite falling short of victory. The party led by Nigel Farage campaigns on immigration control, anti-establishment messaging, and traditional values, attracting disaffected working-class voters. However, converting polling into victories remains challenging as Caerphilly demonstrated.
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