PollCheck, the polling aggregator, published a five-poll rolling average on 1 April 2026 showing Plaid Cymru on 28.4 per cent and Reform UK on 27.6 per cent, with Welsh Labour trailing on 18 per cent. The 0.8-point gap at the top sits comfortably inside any single poll's margin of error, meaning neither lead party can claim a statistical advantage thirty days before polling day.
The aggregate tells a different story from the YouGov seat projection because vote share does not translate linearly into seats under D'Hondt allocation across six-member constituencies. A party needs roughly 12 per cent of a constituency vote to secure a single seat, per the Senedd Research Service. The arithmetic compresses vote share into larger seat swings for the leading parties and punishes those that fall below the threshold in multiple constituencies.
No Welsh election since the founding of the Senedd in 1999 has had a Welsh nationalist party and a UK-wide right-populist party within a point of each other at the top of the aggregate. The race is structurally new: neither Plaid Cymru nor Reform UK is a party of government in Cardiff Bay, and the aggregate places Welsh Labour ten points behind both. The Welsh Liberal Democrats sit outside the projected threshold entirely.
