Plaid Cymru opens up commanding lead as first 2026 Senedd poll predicts political earthquake in Wales

Plaid Cymru has surged ahead as the predicted largest party in May’s Senedd election, pulling well clear of Reform UK and deepening the crisis facing Wales’ traditional political giants, according to the first poll of 2026 from ITV Cymru Wales.

The poll, conducted by YouGov and published less than four months before voters go to the polls, shows Plaid’s vote share climbing from 30% to 37% since September.

Reform UK, which had been neck-and-neck with Plaid throughout 2025, has dropped six points to 23%.

In a landmark shift, the Green Party is now polling third at 13% — its highest ever Welsh showing — with Labour and the Conservatives tied in fourth place on just 10%. Labour has never polled that low in a Senedd election.

The findings suggest Wales could be heading for the biggest political upheaval since devolution began.

Seat forecast puts Plaid within reach of majority government

This Senedd election is the first to use Wales’ new proportional voting system and comes with an expanded chamber of 96 Members.

Modelling the poll results, Cardiff University’s Welsh Governance Centre projects:

Plaid Cymru – 45 seats

Reform UK – 23 seats

Green Party – 11 seats

Labour – 8 seats

Conservatives – 6 seats

A total of 49 seats would be needed for an outright majority, putting Plaid within touching distance of governing alone and on course to lead a non-Labour Welsh Government for the first time in history.

Dr Jac Larner, from Cardiff University’s Welsh Governance Centre said: “This poll shows a stark contrast to previous polling, with a substantial 14-point gap between Plaid Cymru and Reform UK in Senedd voting intention—a significant shift from the two parties appeared neck and neck.

“While any single poll should come with a health warning and this may be something of an outlier, it continues broader trends we’re seeing in Welsh polling, where Plaid Cymru have enjoyed a modest boost, and trends in England, where Reform support appears to be plateauing while the Greens have surged.

“Two patterns are particularly noteworthy. First, the gains for both the Greens and Plaid Cymru appear to be drawing from voters who were previously undecided, rather than coming from other parties. Second, Plaid Cymru seem to be consolidating their position as the party best placed to challenge Reform UK—57% of respondents in our sample identified them as such.”

Adrian Masters, ITV Cymru Wales’ Political Editor said: “While the main headlines from the first poll of 2026 remain the same as those in 2025, there are some significant twists, which will make everyone involved in politics sit up.

“Plaid Cymru’s extended lead, Reform UK’s faltering second place and the Greens’ new third place show that change is in the air and it is now highly likely that the Senedd will see the biggest political change since it came into being as the Welsh Assembly back in 1999. What form that change takes is still to be decided.”

Westminster

The poll also found Plaid now ahead of Reform UK for Westminster voting intentions in Wales:

Plaid – 29% (+6)

Reform – 25% (-4)

Labour – 13% (-5)

Conservative – 12% (+1)

Green – 12% (+5)

Lib Dem – 6% (-3)

That movement coincides with rising approval for Plaid leader Rhun ap Iorwerth and increasing dissatisfaction with Reform’s Nigel Farage.

If replicated in May, the result could bring:

Labour’s first loss of power since devolution in 1999

A Plaid Cymru First Minister for the first time

A possible Plaid-Labour deal — though Labour’s seat tally may make that difficult

Reform UK as Wales’ official opposition

Greens emerging as a major force in the Senedd

Adrian Masters warned that Labour and the Conservatives could face “devastation, literally and emotionally” based on current projections.

About the poll

YouGov surveyed:

1,220 adults (16+) for Senedd voting intention

1,205 adults (18+) for Westminster voting intention
Fieldwork ran from 5–12 January 2026.

With four months to go, parties on all sides will now be bracing for what could become the most unpredictable and consequential Senedd election Wales has ever seen.