the biggest question that should be answers first is : WHY?
what is blockchain? it is a chain of blocks.
what would these blocks regarding votes contain? the votes themselves? why? what would be the point of creating a chain of votes in form of blocks and hold them somewhere? what is wrong with a normal database instead of a blockchain?
or maybe you mean some form of cryptographic proof? that is not blockchain.
it is something else, but who will issue the keys for creating the "vote" cryptographically and how would you prevent people from having multiple keys?
and the final question is that will it be worth all these efforts to replace the old system that works?
I see others saying "it is a good idea" but in my opinion your idea is way too vague and general. you need to explain how will it work and what are the angles then decide if it is a good or a terrible idea. because it can be either.
The why is quite simple, to prevent electoral fraud/Tampering with electronic voting machines. A transparent, hack-proof/secure voting system based on Blockchain eliminates this.
The existing voting system, be it paper-based or e-voting isn't transparent, you cast vote, you aren't sure if your vote was changed or counted. That's why some people abstain from voting. A transparent voting system would restore their trust. So IMO it is definitely worth replacing the existing system.
List of controversial elections,
https://en.m.wikipedia.org/wiki/List_of_controversial_electionsDigital Voting with the use of Blockchain Technology,
https://www.economist.com/sites/default/files/plymouth.pdfThe concept is implementable.