It’s simple: voting privacy.
When you bank online, the security of your interactions with the bank are authenticated (your login password and hopefully some sort of two-step verification passcode), so the bank knows it is YOU on the other end. You have no expectation of privacy from your bank. You expect that your bank will know it’s you who moved money; in fact, you want them to MAKE SURE it’s REALLY YOU that moved that money and not someone else.
When you vote, it’s the opposite — the polling place needs to track whether you voted or not, but they are not allowed to know HOW you voted. If a pollster (or anyone else at the poll for that matter) can know how you vote, it can lead to problems like voter intimidation or voters selling their votes for money (they both have happened). It’s called “secret ballot” for a reason. This would be like an online bank that authenticated you, but then had no idea what your balance was or who you paid.
For someone who isn’t a technologist, voting online would appear perfectly reasonable. Just log me in, let me cast my vote, but don’t track my name to my voting history. However, to do this, the system would have to be 100% perfectly secure so an outside attacker couldn’t steal this information (which is impossible with software) and the operators of the online voting system would have to be 100% trustworthy to never subtly collect your name with your voting history (good luck with that).
For the average person, your passwords, credit card numbers, email address, home address, phone number, and SSN (or other national ID number) have already been collected by hackers and dumped on the internet. Do you really want to add your voting history, too? If you say yes, do you think you’d feel the same in 20 or 40 years? What if you change your mind in the future? What if people who don’t like your voting history choose to harass you?
It may feel old fashioned, but the following two options are the safest ways to maintain “secret ballots”:
A) A paper ballot with automated tabulation (machine counters) backed by statistical sampling to verify, or,
B) Electronic ballot with paper “receipt” that can be validated by the voter, placed into a receptacle at the polling place, and receipts statistically sampled to verify they match electronic ballot results.
The “statistical sampling” is a mathematically provable method for humans to manually count only a subset of the ballots, but guarantee they match the entire population of votes with a high degree of confidence. This step is super important. It’s a blend of the scale that comes from automation with verification from human eyes.
From someone who has made a career breaking into online systems, please do not ask to vote online.
Encourage your polling place to use one of the methods described above.