https://en.wikipedia.org/wiki/Electoral_fraud#Vote_buying
"bring me an ID which shows you voted for X and I'll give you $5"
https://en.wikipedia.org/wiki/Electoral_fraud#Intimidation
"bring me an idea showing you voted for X or you're fired"
https://en.wikipedia.org/wiki/Voter-verified_paper_audit_tra... is the correct-est solution I'm aware of.
for exactly the reasons above.