The latest poll on voting intentions for Thursday’s historic Senedd elections show that Plaid Cymru will be the biggest party in Wales, winning 43 seats – and predicts First Minister Eluned Morgan could lose her seat.

YouGov’s final MRP model of the 2026 Senedd election for ITV Cymru Wales places Rhun ap Iorwerth in pole position to be the next first minister, with a central projection of 43 seats for Plaid Cymru.

This would be just six shy of the 49 needed for a majority in the now 96-member Welsh parliament, and puts them ahead of Reform UK, who are in a strong second place on 34 seats in YouGov’s median estimate.

For both parties, such a result would represent substantial gains on the 2021 election, which would have resulted in 24 seats for Plaid Cymru had it been conducted under the newly introduced electoral system, and zero seats for Reform UK, who won a mere 1% of the vote five years ago.

The latest model, which uses data from more than 4,600 adults in Wales in fieldwork from 25 April to 4 May, suggests Plaid Cymru have made small gains in the latter stages of the campaign, largely at the expense of the Greens.

YouGov says: “Nonetheless, the model overall projects a range of outcomes, with the allocation of some seats by the new D’Hondt voting system on a knife-edge.

“Plaid Cymru hold a lower-end estimate of 36 seats and a higher-end result of 48 seats, while Reform UK has an overall projected range of 31 to 41 seats, including emerging as the largest party in 13% of our simulations.

“Such is the sensitivity of allocations under D’Hondt to minor changes in vote shares that the predicted seat range for each party is relatively wide as a result, reflecting the narrow races in some constituencies.”

This recolouring of the political map is set to come primarily at the expense of Labour, who are set to fall to just 12 members of the Senedd (MSs), a notional loss of 32.

Such is the scale of the defeat for Labour, who have won every devolved election so far and topped the poll in Wales at every Westminster election since 1922, that they do not finish first in any of the Senedd’s 16 constituencies in the forecast, and are set to win zero out of six seats in four of them.

One such constituency is Ceredigion Penfro, in the west of the country, and where Eluned Morgan is top of Labour’s list of candidates, making it a realistic possibility that the first minister will lose her seat.

It’s not just Labour who are being knocked back. While Wales has not been such an area of strength for the Conservatives, the model projects the party will be reduced to just four seats, down from a notional result of 26 in 2021 and their worst result in a devolved election to date.

This would additionally leave the party short of the five seats needed to form a political group in the Senedd, barring them from chairing committees and limiting their ability to question ministers.

The Liberal Democrats are also likely to fall short of this threshold, winning only a single seat on the median projection (in the mountainous Brycheiniog Tawe Nedd constituency), meaning Jane Dodds would remain the party’s sole representative in the Senedd.

Rounding out the chamber, but also likely to be unable to form a group by themselves, are the Greens, who are projected to win their first representation in the Senedd according to the model, with a seat in each of the two Cardiff constituencies.

Who will form the next Welsh government?

With no party projected to win a majority of seats in the Senedd, some form of co-operation between the parties will be required in order for a first minister to be elected, even if parties do not form a full coalition government.

Here, there is little doubt that the balance tips decisively towards the likelihood of a Plaid Cymru-led government, as Reform UK and the Conservatives win a collective right-of-centre majority in a mere 1% of the model’s simulations, suggesting Dan Thomas’s route to being first minister is limited.

While Rhun ap Iorwerth has expressed a preference for forming a minority government of only Plaid Cymru ministers, the model suggests he is likely to require Labour’s assistance for a majority in the Senedd, with the two parties holding a 14-seat majority between them in YouGov’s median estimates.

Reacting to the latest poll, a Plaid Cymru spokesperson said: “This poll reflects what we’re hearing on the doorstep the length and breadth of Wales in the final days of the campaign. People are making up their minds, and they are deciding to vote Plaid Cymru.

“That’s because they know Plaid Cymru is the best way to stand up for fairness for Wales – from the billions owed in HS2 to power over our natural resources. They know that Plaid Cymru will give Wales the new leadership it needs to improve our NHS, tackle the cost of living with our generous childcare offer and unlock our economy’s potential.

“And they know that only Plaid Cymru can stop billionaire backed Reform from taking Wales backwards.

“This poll shows that there is real momentum behind Plaid and that we can win, but with just days to go, nothing can be taken for granted. We are within touching distance of forming the next government, and every vote will help decide the future of Wales.

“Momentum alone won’t deliver change. If you want to stop Reform and choose hope, ambition, and a government that puts Wales first, that change can only come by voting Plaid Cymru on May 7.”

Dan Thomas, Leader of Reform Wales, said: “Tomorrow is a historic opportunity for us to deliver real change here in Wales, but we can only do that if we stop another Labour and Plaid stitch up.

“That’s why we need to deliver a result too big for the political establishment to ignore.

“A vote for the Tories or any other party is a wasted vote, and will let Plaid in.

“Vote Reform to scrap blanket 20mph, end the Nation of Sanctuary and put Welsh families first.”