| District ID | 48th District |
| Representative | Darrell Issa |
| Party Affiliation | Republican |
| Partisan Voting Index (PVI) | R+4 |
| 91901 |
| 91902 |
| 91905 |
| 91906 |
| 91914 |
| 91916 |
| 91917 |
| 91931 |
| 91934 |
| 91935 |
| 91941 |
| 91948 |
| 91962 |
| 91963 |
| 91977 |
| 91978 |
| 91980 |
| 92003 |
| 92004 |
| 92019 |
| 92020 |
| 92021 |
| 92025 |
| 92026 |
| 92027 |
| 92028 |
| 92029 |
| 92036 |
| 92040 |
| 92055 |
| 92059 |
| 92060 |
| 92061 |
| 92064 |
| 92065 |
| 92066 |
| 92069 |
| 92070 |
| 92071 |
| 92078 |
| 92082 |
| 92084 |
| 92086 |
| 92119 |
| 92128 |
| 92131 |
| 92158 |
| 92530 |
| 92536 |
| 92539 |
| 92544 |
| 92562 |
| 92563 |
| 92584 |
| 92590 |
| 92591 |
| 92592 |
| 92595 |
| 92596 |