2021 Senedd election

In elections for the Senedd, each voter has two votes in the additional member system. The first vote is for a candidate to become the Member for the voter's constituency, elected by the first past the post system. The second vote is for a regional closed party list of candidates. Additional member seats are allocated from the lists by the D'Hondt method, with constituency results being taken into account in the allocation. The overall result is approximately proportional.

In accordance to the Wales Act 2014, a candidate is allowed to stand in both a constituency and a regional list. However, holding a dual mandate with the House of Commons is illegal, meaning a Member of the Senedd cannot also be an MP.

This will be the first election where 16 and 17 year olds can vote, following the introduction of a new law in January 2020.[2]

The 2019 European Parliament election in the United Kingdom was the last of its kind. The newly formed Brexit Party came out on top in Wales. Plaid Cymru, who support full Welsh independence, came second, marking the first time it had beaten Labour in a Wales-wide election.[3] The Brexit Party also formed a parliamentary group in the Assembly made up of the 4 ex-UK Independence Party members, lead by Mark Reckless.[4] A snap general election was called for 12 December 2019. Welsh Labour suffered an 8% drop in their vote and they were completely wiped out of North Wales, apart from in Alyn and Deeside. Labour ended up losing 6 parliamentary seats to the Welsh Conservatives in Boris Johnson's landslide victory. These seats included Bridgend, which has been represented on the assembly level by former First Minister of Wales Carwyn Jones since the 1999 election. The Conservatives also picked up Brecon and Radnorshire from the leader of the Welsh Liberal Democrats Jane Dodds.[5]

On 31 January 2020, the United Kingdom left the European Union. This followed a referendum on the matter in which Wales voted to leave the EU.[6] South Wales has been highlighted by many as evidence that Brexit was a cross-party issue, as those areas typically vote overwhelmingly for Labour. Blaenau Gwent, Torfaen, and Caerphilly all voted overwhelmingly in favour of Brexit, but are all represented in the House of Commons of the United Kingdom by Labour MPs.

Plaid campaigned for a remain vote in the 2016 referendum on the UK's membership of the EU.[7] Plaid later supported, during the final stages of Brexit process, a second referendum on the matter.[8][9] Plaid argued that there should be a referendum on Welsh independence after Brexit, so that Wales could apply for EU membership.[10] A June 2020 YouGov/ITV Cymru poll concluded that 25% were in favour of independence and 54% opposed.[11]

The following MSs will not run for re-election:

Below are listed all the constituencies which require a swing of less than 10% from the 2016 result to change hands.

NB: MSs in office (i.e. incumbents) before the election are bolded. Winners are highlighted with party colours.

The constituency vote is shown as semi-transparent lines, while the regional vote is shown in full lines.

Graph of the evolution of the opinion polls for the 2021 Welsh Parliament election (the right border represents the last possible day for the election to be held). Lines represent local regressions (LOESS) with a span of 0.5.

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