I live in Denmark where we have a digital identity called "nenId". It's the safest form of citizen identification we've ever had and it would be immensely more safe for elections than our current system of sending out paper cards to be traded in for a vote.
On top of that the block chain could offer us a record that couldn't be manipulated.
Sure we don't have a lot of problems with voter fraud in our current system, but that doesn't mean it's not extremely vulnerable because it relies on honest counting.
There is no such thing as "safest form" of anything. You have to consider what threats you are trying to defend against. The threats that you have to defend elections against are completely different than anything else. In particular, elections have to defend against a government that tries to stay in power. A centralized form of identification can be the most dangerous thing for an election ever.
On top of that the block chain could offer us a record that couldn't be manipulated.
Sure we don't have a lot of problems with voter fraud in our current system, but that doesn't mean it's not extremely vulnerable because it relies on honest counting.