Below are lists of SDLP marginal seats showing which constituencies won in the latest elections can be most easily lost.
Historical
Below is the SDLP defence list consisting of SDLP 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. | Foyle | Northern Ireland | 4,166 | 5.43% | |
| 2. | Belfast South and Down Mid | Northern Ireland | 12,506 | 14.38% |