| Caerphilly | |
| Constituency Type: | Senedd county constituency |
| Parl Name: | Senedd |
| Year: | 1999 |
| Parts Label: | Electoral region |
| Parts: | South Wales East |
| Member Label: | MS |
| Member: | Hefin David |
| Party Label: | Party |
| Party: | Labour |
Caerphilly is a constituency of the Senedd. It elects one Member of the Senedd by the first past the post method of election. It is additionally one of eight constituencies in the South Wales East electoral region, which elects four additional members, in addition to eight constituency members, to produce a degree of proportional representation for the region as a whole.
The constituency was created for the first election to the Assembly, in 1999, with the name and boundaries of the Caerphilly Westminster constituency.
The other seven constituencies of the South Wales East electoral region are Blaenau Gwent, Islwyn, Merthyr Tydfil and Rhymney, Monmouth, Newport East, Newport West and Torfaen.
In general elections for the Senedd, each voter has two votes. The first vote may be used to vote for a candidate to become the Member of the Senedd for the voter's constituency, elected by the first past the post system. The second vote may be used to vote for a regional closed party list of candidates. Additional member seats are allocated from the lists by the d'Hondt method, with constituency results being taken into account in the allocation.
Regional Ballot void votes: 145. Want of an Official Mark (0), Voting for more than ONE party or individual candidate (71), Writing or mark by which the Voter could be identified (4), Unmarked or Void for uncertainty (145)
Regional ballots rejected at the count: 143[1]
2003 Electorate: 68,152
Regional ballots rejected: 316