With the Senedd election shaping up as a close two-horse race between Plaid Cymru and Reform UK, Survation’s final polling has captured a late swing towards Plaid in the crucial closing days of the campaign. Where Reform held a narrow lead towards the end of April, the picture has now shifted: Plaid sit at the top with 30.3% (up 2.4 points), with Reform UK on 28.2% (down 1.4 points). Labour remain a distant third on 15.3%, unchanged from April.

Plaid Cymru are on course to become the largest party in the Welsh Senedd for the very first time. Our model projects Plaid winning 34 seats (range 30–40), putting them narrowly ahead of Reform UK on 32 seats (28–36). With just two seats separating the parties in our central estimate and overlapping ranges throughout,  Plaid currently hold a 78% probability of finishing first. Labour, meanwhile, are projected to win just 17 seats (range 13–20). If that figure holds, it would represent a dramatic fall from grace for a party that has dominated Welsh politics for a generation. The Conservatives are on course for 6 seats (3–10), with the Greens at 3 (1–6) and the Liberal Democrats at 2 (0–4).

A majority in the new 96-seat Senedd requires 49 seats — a threshold no single party comes close to reaching. That makes the question of coalition arithmetic absolutely central. Our modelling suggests Plaid will hold the balance of power, and any route to a governing majority runs through them. The numbers point clearly towards a Plaid–Labour coalition as the most viable path to government, reaching a majority in 87% of our model’s simulations with a median combined total of 51 seats. Bring in the Greens or the Liberal Democrats and that probability climbs above 97% On the other side of the aisle, Reform and the Conservatives combine for a median of just 38 seats, leaving them well short of the 49 needed and with no obvious route to power.

GET THE DATA.

Survation conducted an online poll of 1,054 adults aged 16+ in Wales. Fieldwork was conducted between 1st – 6th May. Tables are available here.

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