D'Hondt method

The D'Hondt method is a highest-averages seat allocation system for proportional representation elections. A party's vote total is divided by successive integers (1, 2, 3, and so on); seats are awarded sequentially to whichever party has the highest resulting quotient at each step. The method slightly favours larger parties compared to other PR formulas (such as Sainte-Laguë) but remains far more proportional than first-past-the-post. It is used in the European Parliament, the Northern Ireland Assembly, the Scottish Parliament regional lists, and — from 2026 — all seats in the Senedd.

For the 7 May 2026 Senedd election, D'Hondt applied across 16 constituencies, each returning 6 Members of the Senedd (MSs), for a total of 96 seats replacing the old 60-seat Additional Member System chamber. Plaid Cymru won 43 seats (exact match with the YouGov final MRP projection), Reform UK won 34 seats, Welsh Labour 9, Welsh Conservatives 7, Wales Greens 2, and Welsh Liberal Democrats 1. The D'Hondt outcome represented an exact match on Plaid's seat tally and came within the MRP uncertainty band on all other parties — a striking contrast to the 38% English FPTP undershoot for Reform UK on the same night.

The 2026 Senedd election is the first UK electoral contest in which two devolved chambers — Holyrood using AMS, the Senedd using pure D'Hondt — returned results on the same night, creating a direct methodological comparison. D'Hondt's Welsh debut validated the method's predictability under closed-list conditions and will be cited in any future UK debate about electoral system Reform, including the recurring question of whether Westminster should move to a proportional system.