Below are lists of Plaid Cymru marginal seats showing which constituencies won in the latest elections can be most easily lost.
Below is the Plaid Cymru defence list consisting of Plaid Cymru held marginal seats for the 2029 general election. These marginal constituencies are ordered from the smallest to the largest swing to be defeated by the largest opposition party.
View Plaid Cymru target seats for the next general election.
(order by percentage majority)
| Rank | Constituency | Region | Majority | Swing to Defeat | |
|---|---|---|---|---|---|
| 1. | Ynys Mon | Wales | 637 | 0.98% | |
| 2. | Caerfyrddin | Wales | 4,535 | 4.97% | |
| 3. | Ceredigion Preseli | Wales | 14,789 | 15.97% | |
| 4. | Dwyfor Meirionnydd | Wales | 15,876 | 19.65% |
View Plaid Cymru target seats for the next general election.
Below is the Plaid Cymru defence list consisting of Plaid Cymru held marginal seats for the 2026 Senedd election. These marginal constituencies are ordered from the smallest to the largest swing to be defeated by the largest opposition party.
View Plaid Cymru target seats for the next Senedd election.
(order by percentage majority)
| Rank | Constituency | Region | Majority | Swing to Defeat | |
|---|---|---|---|---|---|
| 1. | Carmarthen East and Dinefwr | Mid and West Wales | 6,813 | 10.24% | |
| 2. | Dwyfor Meirionnydd | Mid and West Wales | 7,096 | 14.90% | |
| 3. | Ynys Mon | North Wales | 9,817 | 17.70% | |
| 4. | Ceredigion | Mid and West Wales | 12,145 | 19.74% | |
| 5. | Arfon | North Wales | 8,652 | 19.89% |
View Plaid Cymru target seats for the next Senedd election.