Plaid Cymru Surges to Lead in Welsh Senedd Poll, Threatening Labour Dominance

Key facts

• Plaid Cymru leads with 33% vote share, four points ahead of Reform UK at 29%.
• YouGov MRP modelling for ITV Cymru Wales projects Plaid Cymru winning 43 seats, Reform UK 34.
• Labour polls at 12%, yielding 12 seats but not for Welsh leader Eluned Morgan.
• Welsh Conservatives at 9% would win four seats; Green Party at 8% would win two.
• Welsh Liberal Democrats at 6% would elect leader Jane Dodds in Brycheiniog Tawe Nedd.
• 43% of respondents believe Plaid Cymru will lead the next Welsh government.
• 44% of voters prefer a single-party government over a coalition (32%).

Plaid Cymru's Unexpected Ascent

Two days before polls open in the Senedd Election, a new ITV Cymru Wales opinion poll has placed Plaid Cymru as the projected largest party, upending decades of Labour dominance in Wales. The survey, conducted by YouGov in partnership with Cardiff University, gives Rhun ap Iorwerth's party 33% of the vote share, four percentage points ahead of Reform UK at 29%. Under the newly implemented d'Hondt voting system, this vote share would translate into 43 seats for Plaid Cymru and 34 for Reform UK, according to the MRP modelling. The poll underscores how small shifts in vote share can produce outsized seat gains under the new electoral rules, a dynamic that has reshaped the campaign's final stretch.

Labour's Historic Decline

Labour, which has governed Wales since devolution, continues its downward trajectory, polling at just 12% — a figure that would yield 12 seats but not for Welsh leader Eluned Morgan. The party's third-place standing marks a dramatic fall from its traditional dominance, reflecting broader voter discontent and the fragmentation of the Welsh political landscape. The Welsh Conservatives have seen a modest increase to 9%, placing them fourth, which would translate into four seats. The Green Party has dropped to fifth place at 8%, a level that in this scenario would net them only two seats, in Caerdydd Ffynnon Taf and Caerdydd Penarth.

Volatility and the New Electoral System

The poll's findings highlight the volatility inherent in the new d'Hondt system, where small vote share differences can dramatically alter seat counts. Labour, the Conservatives, and the Greens are all polling within a range where a few percentage points either way could have a huge impact on constituency outcomes across Wales. For the Greens, the drop in seats could be reversed if just a few thousand more votes go their way in the constituencies where they are most competitive but not currently projected to win a sixth seat. The Welsh Liberal Democrats, holding steady at 6%, would elect their leader Jane Dodds in Brycheiniog Tawe Nedd.

Public Sentiment and Coalition Preferences

Beyond voting intentions, the poll reveals that 43% of respondents believe Plaid Cymru will end up leading the next Welsh government — by far the most popular opinion. In contrast, only 15% think Reform UK will lead the government, despite its strong second-place showing. The survey also found that 44% of voters would prefer the next government to be formed by a single party, while 32% favor a coalition of multiple parties. This preference for single-party rule could complicate coalition-building if no party secures an outright majority, a likely scenario given the fragmented vote.

Outlook and Stakes

As polling day approaches, the race remains fluid. The MRP modelling is just one scenario, but it demonstrates how a small vote share increase can have a huge impact on projected seats. The final outcome will depend on turnout and last-minute shifts, particularly in key constituencies where margins are razor-thin. For Labour, the stakes could not be higher: a third-place finish would be an unprecedented rebuke, potentially triggering a leadership crisis. For Plaid Cymru, the poll represents a historic opportunity to lead Wales for the first time, though forming a stable government may require navigating coalition negotiations or seeking confidence-and-supply arrangements.

The bottom line

• Plaid Cymru leads the final pre-election poll with 33%, projected to win 43 seats under d'Hondt.
• Reform UK surges to second at 29%, projected 34 seats, while Labour collapses to third at 12%.
• The new electoral system amplifies small vote share changes into large seat swings.
• 43% of voters expect Plaid Cymru to lead the next government; only 15% say Reform UK.
• A majority of voters prefer single-party government, complicating potential coalitions.
• Labour's Welsh leader Eluned Morgan would not retain her seat under current projections.