Vote selling also doesn't occur in that sentence. There's a reason we don't tear off a hash from a ballot right now to be given to voters, enabling them to verify later their hand counted ballot wasn't discarded or used to vote for somebody else, because it enables vote selling since now you have proof you voted for a candidate. Foreign superpowers could even automate this with a smart contract. Upload a signed txn proving you voted how they want you to and collect your $100 worth of coins. SuperPACs with hundreds of millions of advertising dollars would cancel ads and buy your vote.

Zero knowledge proofs can solve this.