Below are lists of Sinn Fein marginal seats showing which constituencies won in the latest elections can be most easily lost.
Historical
Below is the Sinn Fein defence list consisting of Sinn Fein held marginal seats for the 2029 general election based on the 2024 boundaries. These marginal constituencies are ordered from the most vulnerable seats to the safest.
| Rank | Constituency | Region | Majority | Swing to Defeat | |
|---|---|---|---|---|---|
| 1. | Fermanagh and South Tyrone | Northern Ireland | 4,571 | 4.47% | |
| 2. | Belfast North | Northern Ireland | 5,612 | 6.94% | |
| 3. | Down South | Northern Ireland | 9,280 | 10.26% | |
| 4. | Ulster Mid | Northern Ireland | 14,923 | 16.42% | |
| 5. | Newry and Armagh | Northern Ireland | 15,493 | 16.86% | |
| 6. | Tyrone West | Northern Ireland | 15,917 | 18.21% | |
| 7. | Belfast West | Northern Ireland | 15,961 | 20.08% |