Plaid Cymru By-elections
| Election | Constituency | Candidate | Vote count | Vote share | Position |
| 4 April 2019 | Newport West | Jonathan Thomas Clark | 1,185 | 5.0% | 4th |
| 5 May 2016 | Ogmore | Abi Thomas | 3,683 | 15.8% | 3rd |
| Election | Constituency | Candidate | Vote count | Vote share | Position |
| 4 April 2019 | Newport West | Jonathan Thomas Clark | 1,185 | 5.0% | 4th |
| 5 May 2016 | Ogmore | Abi Thomas | 3,683 | 15.8% | 3rd |