Who administers the election in which you are interested? Are you looking nation wide? It all depends on state election law as to who will have the information. I know that the Secretary of my State has the information, but I don't know if they have all that information available to me unless I file an open records request. My county also has it since they administer the elections.
It looks like in Florida, the SOS has it. Having a summary of all the categories like age, sex, gets pretty cumbersome to put together. But it looks like race is alive and well in Fla. Pick an election.
http://election.dos.state.fl.us/voterreg/vrArchive/2006voterreg.shtml