I'd expect a voting system to be unable to prove that any one voter voted in a certain way. I don't think that requirement is well suited for a blockchain?
There are a couple solutions to this. The simplest one could be for the government to publish a known public-key. Vote-data would be encrypted with the public key which only the election board has the private key to decrypt. This would ensure that no citizen could vote twice, each vote could be tracked to where, when, who, but not _what_, except by the election board.