One of the characteristics of a secret ballot is that others can’t tell how you voted. This might protect voters from harassment or intimidation, but it also prevents voters from providing assurance to others about how they voted. A voter might have claimed to have voted a certain way, but the secret ballot means that others can never be sure.
The secret ballot is a barrier to voters selling their votes because the purchaser cannot be certain that the seller voted as promised. Mail-in voting reduces this impediment to selling one’s vote. The purchaser can watch the voter complete the ballot,
