You could probably do it ok if you are not too worried about privacy - log in and say I vote A and they have a ledger saying Tim voted A and can email me to confirm. People who are worried can always go to the polling booth and do the paper thing.
Voting is predicated on privacy, to prevent being unduly influenced.
Tsk tsk governments, the blockchain has been mature for close to a decade. You know, the shared ledger that cannot be manipulated.
Blockchain is not a Universal Cure for Everything[tm]. It's not even
a solution for voting.