Two of Wales’ most prominent election experts on what we learnt in the Senedd Election 2026
Rhun ap Iorwerth’s Plaid Cymru was the biggest winner in the(Image: Welsh Government /PA Wire)
By Dr Jac Larner and Professor Laura McAllister
No need to be grateful for the interest of journalists and correspondents from across the UK and the world in Wales these past few weeks. It’s long overdue, and plenty of us warned that the story of these elections would be the Senedd elections — and so it proved. But what does that Welsh lens show us, not just for Wales, but for the UK more widely?
The first answer is that it confirms the end of the traditional two-party system dominated by Labour and the Conservatives (not that this ever truly described Welsh politics, and certainly not Senedd politics!) We’ve long known that the patterns of party alignment and loyalty were eroding.
Voters are more transactional, have more choice, and are certainly exercising it.
Early analysis of survey data suggests that almost half of all voters cast their ballot for a different party than they did in 2021. Those movements, followed the logic of consolidation, not conversion: voters sorted themselves more ruthlessly into two competing blocs rather than crossing the fundamental divide between them.
A majority of those who voted Conservative in 2021 switched to Reform UK. Nearly the same number of 2021 Labour voters moved to Plaid Cymru.
Only approximately 10% of Labour’s 2021 voters went to Reform: the clearest evidence that this was a story of within-bloc realignment rather than wholesale cross-party migration.
We are now in an era of multi-party politics. How that plays out depends on the electoral system in use.
The same parties are not always equally competitive in each component nation of the UK. More proportional electoral systems better reflect the choices of the electorate. However, even proportional systems’ outcomes can be distorted, especially when there are two prominent blocs on the progressive left and the centre right, as there were in Wales in this election.
The much-maligned Closed List PR system using D’Hondt benefitted the two biggest parties as predicted, it’s just that Labour wasn’t one of them.
Looking at the bloc picture over time clarifies what happened. The progressive bloc— Labour, Plaid Cymru, Liberal Democrats, Greens — still commands a majority, finishing with around 58% of the vote to the conservative bloc’s 40%, a gap of 17.6 percentage points.
But this, of course, masks a profound internal restructuring. For our free daily briefing on the biggest issues facing the nation, sign up to the Wales Matters newsletter here
Within the right bloc, Reform UK consolidated what was previously a Conservative vote: its share rose between 21 and 31 percentage points in every single constituency, while the Conservatives fell by between 4 and 22 points everywhere.
Within the progressive bloc, the same logic operated in Plaid’s favour: gains of between 8 and 23 points across Wales, while Labour haemorrhaged support universally, losing between 12 and 34 points.
Blaenau Gwent Caerffili recorded the sharpest Labour collapse at 33.6 points; Pontypridd Cynon Merthyr was close behind at 33.1.
Even in Cardiff, where Plaid’s gains were most dramatic — 23 points in Caerdydd Ffynnon Taf — Labour was retreating at a similar pace.
Complaining that parties ‘game’ the system by claiming it is a two-horse race is risible. Any electoral system can be ‘gamed’ and tactical voting is possible in any system.
Moreover, parties will naturally and understandably use any tactical advantage at their disposal. Just because it was Plaid Cymru and Reform UK using this narrative shouldn’t obscure the fact that most other parties have used it at some point too.
Tactical voting is usually within the same bloc and the evident blocs on the left and right here, alongside an intense polarisation of politics, resonated with electors who were motivated to vote against as much as for.
That same dynamic produced some striking distortions in how votes translated into seats. What matters under D’Hondt is concentration, not volume.
This rewards parties that can aggregate support efficiently and punishes those who spread it thinly.
Reform benefited from consolidating the right-of-centre vote so comprehensively that the Conservatives were left with too little to contest with.
Several parties, meanwhile, came agonisingly close to further seats: Labour in Blaenau Gwent needed just 246 more votes for an additional MS; Reform in Fflint Wrecsam needed only 317. In Caerdydd Ffynnon Taf, Reform and Plaid were simultaneously within touching distance of an extra seat, separated from it by 738 and 594 votes respectively.
The difference between transformative and modest representation in individual constituencies came down to margins that a single motivated street might have produced.
These elections also ended any notion of geographical heartlands for each party. Welsh Labour has huge and embarrassing gaps on the national map.
Meanwhile, the two biggest parties are represented everywhere. For Plaid Cymru in particular, the transformation is remarkable: the party won three seats — half of the total — in each of the two Cardiff mega-constituencies.
Six seats in the capital are more than Plaid has ever held on Cardiff Council. There is no more chastising Plaid as the party of the Welsh-speaking north and west; the party of Wales is now, well, the party of Wales, with a presence from Wrexham to Tenby, from Bangor to Bridgend.
The political repercussions of all this are for another article, but they are not minor.
Wales faces government formation in a Senedd where no bloc commands a majority, where the largest party on the left is not Labour for the first time in the devolved era, and where the party best placed to lead a progressive administration must simultaneously reconcile an urban surge with its Welsh-speaking heartland identity.
The perfect storm of a new electoral system, double incumbency for Labour in London and Cardiff, and a competitive and deeply polarised political environment did for the two traditionally dominant parties and opened the door to two parties well positioned to take advantage.
What neither of those parties has yet had to demonstrate is whether they can govern. That is now the big question.