Really? How do you audit or control for who shows up to vote? Do you check some kind of government ID or can anyone simply vote by claiming they are who they say they are?
Each California county maintains a list of registered voters. Every voter gets sent a ballot in the mail, but is also allowed to vote in person. The consequences of this are that every single ballot and voter are tracked carefully.
Additionally, a person can vote anywhere in a county, so all in-person voting sites maintain connectivity to that somebody doesn't go to multiple voting sites and vote multiple times, in addition to tracking the mail-in ballots.
When voting in person, you provide your name, address, and sometimes age, etc. in order to disambiguate you as the particular person.
Mail-in vote counting happens with outside observers watching, with verified signatures.
So the system protects against each registered voter only voting once.
Registration of voters is usually tied to driver's licenses, when you file a change of address you can check a box to have your registration updated. If you're a new voter, you can provide or drivers license, or if not, the county will follow up with you to obtain other information to ensure that you're not registered by other means and are in fact a real person with that name and address.
> anyone simply vote by claiming they are who they say they are?
Of course they can! That's only just and fair.
If you tried to steal somebody else's identity and vote as them, that would get flagged for multiple voting. Additionally, local political campaigns get lists of every registered voter, as well as which elections they voted in and party affiliation (if they chose one), which they use to campaign and knock on doors. Campaigns have sophisticated information systems to ensure that they don't bother the same voter multiple times, to indicate likelihood of voting and whether the canvasser thought the voter was going to vote for their candidate, etc. If there were a batch of fake voters somewhere, that would show up pretty quickly in these campaigning efforts.
I can't speak for California, but here in my area of NY you show up, give your name and address, which they find in the registered voters list, and you sign on an iPad that gets checked against the signature on file. Then you get handed a ballot. By the local volunteers who are mostly people from the neighborhood, plus observers from both major parties. Your neighbors are there checking in alongside you.
Getting past all this risks years in jail for... an extra vote in a safely blue state.
None of this requires an ID, in part because in the US, there's no law that you have to have an ID in the first place. "Papers, please!" used to be a derogatory thing about totalitarian regimes.
(More practically, if we Dems were rigging elections, we'd win more often.)
If the person you're impersonating shows up to vote too, then that will be noticed and there will be questions. If they don't, there are still opportunities to notice issues after the fact. Get a list of who voted, call a random sample and ask if they actually voted. Check for dead people or noncitizens.
There isn't a ton of checking in advance but that doesn't mean we can't know if the results are legit. If there was a concerted, large-scale effort to impersonate voters, it could be done, and it would seriously screw things up. But it would not go undetected.
You just don't require ID to know this. Voter ID is a very new construct and we don't need it, period. We already know who is and is not registered to vote and the voter registration process is pretty secure.