From your link~I know because I have to show ID to vote always.
Every voter in California is required to provide a driver's license number or state identification number at the polls, but a voter does not have to present a physical form of identification.
If a voter does not have a driver's license or state ID, he or she may use the last four digits of his or her Social Security number. If the voter does not have a Social Security number, the state will assign a unique number that can be used for voting purposes.
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If a voter does not have driver's license or state ID..." means you don't have to have ID with you.
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If the voter does not have a Social Security number...
" means you don't have to have SS neither.
If you don't understand meaning of IF, oh boy, you're really dumb.