California passed "Motor Voter" laws back in the 1990s. What this law did was automatically register the licensee to vote when they got or renewed a California driver's license.
Two years ago, they passed a new law--or just authorized, not 1005 sure, but, Governor Brown allowed illegal aliens to get California drivers, and accept Mexican DL to get new Californian ones without a retest--and, more importantly, no legal sanctions for doing so, thus making California a Sanctuary State. Motor voter registered all these illegals to vote. There's no real mechanism to stop them from voting. Say your name is Hectorio Hernandez and you are an illegal from La Paz, Baja California. Make it to USA California and then trade your Mexican license for a Californian license. Now, come Election day, you go to the polling place, show your California license, they look you up on the roster, you're registered, they then hand a ballot. The cannot ask you your legal status, or, at least in California, won't. Easy peasy.
Not legally. You must check a box confirming you are a US citizen in order to register legally.
A total of 12 states plus the District of Columbia allow undocumented immigrants to obtain a driver's license. These 12 states include California, Colorado, Connecticut, Delaware, Hawaii, Illinois, Maryland, New Mexico, Nevada, Utah, Vermont and Washington. Notice that all of them went Dem.
I am just as concerned about the 15 million or so green card holders (Legal Permanent Residents) who have SSNs, drivers licenses, etc. The only thing they can't do is vote legally. However, we know that many of them are by claiming to be citizens on the registration forms. With a few exception, none of the states require proof of citizenship when registering to vote.