The 2026 Senedd election, scheduled for Thursday 7 May, will be one of the most important contests in the modern political history of Wales.
A major overhaul of the electoral system has transformed the landscape ahead of polling day. The Welsh Government’s move from a mixed system – combining constituency-based first-past-the-post mandates with regional list representation – to a fully proportional, region-based model is expected to end the one-party majority in the Senedd. The increase in the number of members has further complicated direct comparisons with previous elections.
Recent election evidence points to a fragmented and highly competitive race. In last year’s by-election, Welsh Labor came third in their traditionally safe seat of Caerphilly. Analysts noted a split in the working-class vote, fueled by concerns over the cost of living and immigration. Both Plaid Cymru, which won the seat, and Reform UK drew support from different segments of Labour’s traditional base.
Polls since then have only confirmed the Caerphilly narrative: Labor are far behind, with Plaid and Reform battling for first.
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Across Wales, Labour’s position appears to have weakened significantly. Forecasts show the party could be on track for one of its weakest performances in more than a century. Her gains in North Wales in the 2024 general election now look within reach, while in parts of South Wales – including around Cardiff – competition from smaller parties has added further uncertainty.
The Green Party of England and Wales, although historically underrepresented in the Senedd, is in some scenarios expected to secure its first members under the new proportional system. Meanwhile, the Welsh Conservatives are also expected to face defeat, reflecting a wider reshaping of the political balance.
According to the Britain Predicts model, Plaid Cymru is in the best position to emerge as the largest party, potentially leading the Welsh government for the first time. A nationalist party leading the administration in Cardiff Bay would mark a historic change. However, coalition building will be essential, as no party is expected to command a majority. Both progressive and center-right alliances remain arithmetically possible.
Country by country forecast
At the electoral and regional level, the forecasts point to a very competitive and unpredictable map. Many fields will be won by narrow margins.
The Britain Predicts model applies the same methodology that underpinned its 2024 predictions, combining demographic data, national survey trends and historical patterns of over- and under-performance. He distinguishes between the more fickle “swing” voters and those with entrenched party loyalties – although the latter appear to be waning. The model does not involve internal assumptions or subjective adjustments. Instead, it provides a transparent, data-driven projection of how votes might translate into seats under the new system.
Structural reform, changing voter behavior and a fragmented party system combine to mean that the 2026 Senedd election is poised to redefine Welsh politics – regardless of which party ultimately comes out on top.
(Further reading: Britain can no longer afford to be middle class)
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